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Biology
Tr
8
Pearson Foundation Series
CLASS
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CLASS
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Pearson Foundation Series
Biology
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Brief Contents
Prefacexi
Chapter Insights
xii
Series Chapter Flow
xiv
Chapter 1Cell—The Basic Unit of Life
1.1
Chapter 2
Tissues and Body Movements
2.1
Chapter 3
Classification of Living Organisms
3.1
Chapter 4
Reproduction in Animals and Plants
4.1
Chapter 5
Microorganisms and Human Health
5.1
Chapter 6
Ecosystem and Biodiversity
6.1
Chapter 7
Food—Production and Management
7.1
Supplement Reading: Scope of Science
S.1
This page is intentionally left blank.
Contents
Prefacexi
Chapter Insights
xii
Series Chapter Flow
xiv
Chapter 1 Cell—The Basic Unit
of LifeP1.1
IntroductionP1.2
Cell—the Basic Unit of Life
P1.2
Discovery of Cell
P1.2
Unicellular and Multicellular Organisms
P1.3
Cell Theory
P1.3
Size of Cell
P1.4
Shape of Cell
P1.4
Types of Cells
P1.5
Prokaryotic Cells
P1.5
Eukaryotic Cells
P1.8
Cell Organelles
P1.10
Various Organelles and their Role in Cell P1.16
Cell Division
P1.17
Cell Division in Prokaryotes
P1.17
Cell Division in Eukaryotes
P1.18
MitosisP1.18
MeiosisP1.19
Practice Questions
P1.22
Hints and Explanation
P1.25
Chapter 2 Tissues and
Body MovementsP2.1
IntroductionP2.2
Plant Tissue
Meristematic Tissue
Permanent Tissue
Simple Permanent Tissue
Complex Permanent Tissues
Epidermal Tissue
P2.2
P2.2
P2.3
P2.3
P2.5
P2.6
Animal Tissue
Epithelial Tissue
Connective Tissue
Muscular Tissue
Nervous Tissue
Body Movements
P2.6
P2.7
P2.8
P2.10
P2.11
P2.12
CiliaP2.12
FlagellaP2.12
Pseudopodia (False Feet)
P2.13
MusclesP2.13
Skeletal System
P2.14
Axial Skeleton
P2.14
Appendicular Skeleton
P2.14
JointsP2.15
Practice Questions
P2.16
Hints and Explanation
2P.19
Chapter 3 Classification of
Living OrganismsP3.1
IntroductionP3.2
Hierarchy of classification
P3.2
Binomial nomenclature
P3.3
Universal Rules of Nomenclature
Need for Binomial Nomenclature History of Classification
P3.4
P3.4
P3.5
Aristotle’s Classification
P3.5
Two-kingdom Classification P3.5
Linnaeus Two-kingdom Classification
P3.5
Three-kingdom Classification
P3.6
Five-kingdom Classification
P3.6
MoneraP3.7
ProtistaP3.8
FungiP3.8
PlantaeP3.9
AnimaliaP3.10
viii
Contents
Practice Questions
P3.16
Hints and Explanation
P3.19
Chapter 4 Reproduction in
Animals and PlantsP4.1
Seed Formation
Seed Dispersal
Seed Germination
Practice Questions
P4.26
Hints and Explanation
P4.31
Introduction P4.2 Chapter 5 Microorganisms
Reproduction in Animals
P4.2
Asexual Reproduction
P4.2
Binary Fission
P4.2
BuddingP4.2
FragmentationP4.3
Sexual Reproduction P4.3
Male Reproductive Organs
P4.3
Female Reproductive Organs
P4.5
Ovum or Egg
P4.6
FertilizationP4.6
Types of Fertilization
P4.7
Development of Zygote to Embryo
P4.7
Stages of Human Reproduction
P4.8
And Human HealthP5.1
IntroductionP5.2
Useful Microorganisms
Microorganisms in Food Industry
Microorganisms in Medicinal Industry
Microorganisms in Agricultural Practices
Microorganisms in Commercial Industries
Reproduction in Plants
P4.15
Asexual Reproduction
P4.15
Spore Formation
P4.15
Vegetative Propagation
P4.15
Natural Methods of Vegetative
PropagationP4.15
Artificial Methods of Vegetative
PropagationP4.17
Sexual Reproduction in Plants
P4.19
Structure of Flower
P4.19
Stamen or Androecium
P4.20
Carpel or Gynoecium
P4.21
PollinationP4.21
Natural Pollination
P4.21
Artificial Pollination
P4.22
FertilizationP4.23
P5.3
P5.3
P5.4
P5.5
P5.5
Harmful Microorganisms
P5.5
Human Health and Immunity
P5.6
Immune System
Components of Immune System
Working of Immune System
P5.7
P5.7
P5.7
Growth and Development in Human
beingsP4.8 Human Diseases
InfancyP4.8
ChildhoodP4.8
Adolescence and Puberty
P4.8
Role of Hormones
P4.9
Hormones in Puberty
P4.10
Menstrual Cycle in Females
P4.11
AdulthoodP4.11
Old Age
P4.11
Viviparous and Oviparous Animals
P4.12
MetamorphosisP4.12
P4.23
P4.24
P4.24
Type of Diseases
Infectious Diseases
Non-infectious Diseases
Drug and Alcohol Abuse
Ways to Maintain Proper Health
P5.8
P5.9
P5.9
P5.9
P5.10
P5.10
Practice Questions
P5.13
Hints and Explanation
P5.15
Chapter 6 Ecosystem and
BiodiversityP6.1
IntroductionP6.2
Components of an Ecosystem
P6.2
ProducersP6.2
ConsumersP6.2
Decomposers P6.3
Food Chain and Food Web
P6.3
Trophic Levels
P6.3
BiomagnificationP6.4
Natural Resources
Renewable Resources
Non-renewable Resources
Depletion of Natural Resources
Fossil Fuels
P6.5
P6.5
P6.5
P6.6
P6.6
Contents
CoalP6.6
PetroleumP6.7
Conservation of Fossil Fuels
P6.8
ForestsP6.8
Importance of Trees
P6.8
DeforestationP6.9
Conservation of Forests
P6.9
ix
SowingP7.4
Addition of Manure and Fertilizers
P7.4
Irrigation P7.5
Types of Irrigation
P7.5
WeedingP7.6
Harvesting P7.7
Storage 7.8
PollutionP6.10 Plant Improvement Programmes P7.10
Air Pollution
Effects of Air pollution
Steps to Control Air Pollution
Water Pollution
Effects of Water Pollution
Steps to Control Water Pollution
Soil Pollution
Effects of Soil Pollution
Steps to Control Soil Pollution
P6.10
P6.10
P6.10
P6.11
P6.11
P6.11
P6.11
P6.12
P6.12
BiodiversityP6.14
Biodiversity Hotspot Threat to Biodiversity
Wildlife and its Conservation
P6.14
P6.15
P6.15
In Situ Conservation P6.16
National Parks
P6.16
SanctuaryP6.17
Biosphere Reserve
P6.17
Ex Situ Conservation
P6.18
Zoological Garden
P6.18
Botanical Garden
P6.18
Threatened Species and Red Data Book
P6.19
Important Days in Nature Conservation
P6.21
Main Organizations Related to
ConservationP6.21
HybridizationP7.10
Genetic Engineering
P7.10
Animal Husbandry
P7.11
Dairy Farming
P7.11
Poultry Farming
P7.12
Types of Chickens
P7.13
SericultureP7.13
Life Cycle of Bombyxmori
P7.13
Production of Silk
P7.14
ApicultureP7.14
PiscicultureP7.15
Animal Breeding
P7.15
Draught Animals
P7.16
Green Revolution
P7.17
Animal Diseases
P7.17
Livestock Diseases
Poultry Diseases
Silkworm Diseases
Honeybee Diseases
Fish Diseases
P7.17
P7.17
P7.17
P7.18
P7.18
Useful Microorganisms
P7.18
AlgaeP7.18
FungiP7.19
BacteriaP7.19
Practice Questions
P6.23
Practice Questions
P6.21
Hints and Explanation
P6.26
Hints and Explanation
P6.24
Chapter 7 Food—Production
And ManagementP7.1
Introduction P7.2
Supplement Reading: Scope of
ScienceS.1
IntroductionS.2
CropsP7.2 ScienceS.2
Agricultural Practices
P7.3
PloughingP7.3
Advantages of Ploughing
P7.3
Tools Used for Ploughing the Field
P7.4
Branches of Science
S.2
How do Scientists Work?
S.2
ObservationS.2
Asking Questions
S.3
HypothesisS.3
x
Contents
ExperimentationS.3
Data Analysis and Conclusion
S.4
Communicate Results
S.4
Work of a Scientist: An Example
S.4
Famous Scientists and their Contributions
S.5
Science in Everyday Life
S.6
Science for Human Welfare
S.6
Future of Science
S.7
Preface
Pearson Foundation Series has evolved into a trusted resource for students who aspire to be a
part of the elite undergraduate institutions of India. This new Biology series is an addition to
the existing Foundation series particularly targeted for Medical and other related examinations.
Each title in this series providing authentic and class-tested content for effective preparation—
strong foundation, and better scoring.
The structure of the content is designed in such a manner that it motivates students to go
beyond the usual school curriculum, and acts as a source of higher learning to strengthen the
fundamental concepts of Biology.
The core objective of the series is to be a one-stop solution for faster and effective preparation
for various competitive examinations. Irrespective of the field of study that the student may
choose to take up later, it is important to understand that Mathematics and Science form the
basis for most modern-day activities. Hence, utmost effort has been made to develop student
interest in these basic blocks through real-life examples, critical thinking skills, and asking
questions based on application-analyze from the key concepts. Ultimately, the aim is to ingrain
the art of problem-solving in the mind of the reader.
To ensure high level of accuracy and practicality, this series has been authored by a team of
highly qualified teachers with a rich experience, and are actively involved in grooming young
minds. That said, we believe that there is always scope for doing things better and hence invite
you to provide us with your feedback and suggestions on how this series can be improved
further.
apter
Chapter
Cell—The
1 1
basic
Cell—The
basic
Chapter
Insights
Unit of life
Unit of life
Remember section will
help them to memories
Before beginning this chapter, you should be able to:
and review the previous
ReMeMbeR
• Recall the basic features of a cell
on a particular
Before beginning this chapter, you should be ablelearning
to:
• Remember the meaning and organization of tissue
topics
• Recall the basic features of a cell
ReMeMbeR
5.4
Chapter 5
keY IDeas
• Remember the meaning and organization of tissue
keY IDeas
After completing this chapter, you should be able to:
i
Understand the role of cell in maintaining life
Key points will •help
Info Box!
After completing this chapter, you should be able to:
•
Identify the different cell organelles and their functions
the alga)
students
to identify
Chlorella (a green
is
• Understand the role of cell in maintaining life
taken as a food supplement.
• Diff
between mitosis and meiosis
the essential points
inerentiate
a
Tissues the
and diff
Body
Movements
2.11 and their functions
• Identify
erent
cell organelles
chapter
• Differentiate between mitosis and meiosis
Nervous Tissue
F I g . 5 . 3 Vinegar, produced by the action of bacteria, is used for pickling
Cells of nervous tissue are called neurons. Neurons transmit information through electrical and
chemical
signals. Brain, spinal cord
and nerves are made
up of neurons. Neurons are protected by
microorganisms
in medicinal
Industry
another type of cell called neuroglial cell. Neurons consist of three major parts:
Concepts are
explained in a well
structured and
lucid manner
Microorganisms are used to make antibiotics. These antibiotics are used to kill or stop the growth
other
disease-causing
microorganisms.
1.of Cell
body:
Contains nucleus
and cytoplasm. A simple example is penicillin. Penicillin can be
from thepart
fungus
Penicillium.
These
canbody.
be used to cure many diseases that are
2.obtained
Axon: Longest
and carries
impulses
awayantibiotics
from the cell
3.caused
Dendrites:
Short and branched
partsviral
arising
from theMicroorganisms
cell body. They carry
impulses
to- in the proby microorganisms,
(except
diseases).
can also
be used
wards cell
body. A vaccine is a biological preparation that consists of either dead or weakened
duction
of vaccine.
microbes. When a vaccine is introduced into the body, the body produces antibodies against the
vaccine, which remains
in the body and protects the body from attack by the same microbe in
Mitochondrion
the future. The common examples are rabies and tuberculosis vaccines.
INTRODUCTION
Nucleus
Info Cell
boxes
body
are some
add-on Dendrite
information
on related
topics
i
Axon
terminal
Myelin
sheath
Info Box!
Node of
Synapse
ranvier
There
are more bacterial
Schwann
cells in human body
cell than
human cells!
Axon
and some are non-living. However, both living and non-living things are
composed of certain basic chemical elements, such as Carbon, Hydrogen,
Oxygen and Nitrogen. These chemical elements are found in an organized
manner in the form of cells in the living beings, which distinguishes them
from non-living. Cells are the basic structural and functional units of life. A
cell is the smallest individual unit of matter capable of performing all essential
life processes by itself.
1. Define tissue with one example.
Groups of cells either similar or dissimilar and which perform a specific function are called tissue. for
example, muscular tissue in humans aids in movement and locomotion.
F I g . meristem
5 . 4 Medical
containing
2. Differentiate between apical
and vials
lateral
meristemvaccines
i
Meristems are the plant tissues that can divide throughout their life.
Sir Alexander Fleming was the person who introduced to the world, the greatest
Info Box!
apical meristem
lateral‘Penicillin’.
meristem It saved the lives of thousands
discovery of that time, the antibiotic
of soldiers
during
second Seen
world
war.theHe
wasofawarded
the the
Nobel
Seen
tips of roots
andthe
shoots
along
sides
the stem and
root Prize in
Antibodies are the
sub-at the growing
stances producedIncreases
by the the length
Physiology
or Medicine
alongIncreases
with Florey
andofChain
in the year 1945. Florey
of root and
stem
the girth
plant body
body to fight against foreign
and growth
Chain developed
to produce
penicillin
in sufficient
Involved in primary
of plants processes
Involved
in secondary
growth
of plants quantites to
particles called antigens.
become widely available.
QUICk ReCaP
F I g . 2 . 2 1 A typical neuron showing all parts
Quick Recap
section will
help to review
all important
concepts,
discussed in
that particular
chapter
Chapter Insights
Chapter 4
4.20
xiii
Stigma
Anther
Style
Stament
Each section contains detailed diagrams,
images, real life microscopic views for
better understanding and conceptual
clarity.
Petal
Filament
Sepal
Ovule
Receptacle
1.22
Chapter 1
Pedicel
TesT YOUR CONCePTs
1. The first living cell was discovered by ________
2. ________ is the basic structural and functional
unit of life.
3. Take the odd one out.
Amoeba, Bacteria, Plant, Honeybee.
4. The concept ‘Omnis cellula e cellula’ was put forward by ________.
5. The term ‘protoplasm’ was coined by ________.
6. The smallest cell is ________.
Different levels of
questions have been
(i) Amoeba Stamen or Androecium
(ii) Neuron
included in the Test
(iii) WBC
(iv) RBC
Stamen is the male reproductive organ of a flower and male
gamete
is produced
inside the stamen.
Your
Concept
as well
(a) (i) only Stamen has two(b)
(i) and
(ii) and filament
parts:
Anther
as on Mastering the
(c) (i) and (iii) 1. Anther:(d)
(ii),structure
(iv)
It is(i),the
bearing pollen grains located at the top of the filament of staConcepts which will
men. where ________ is/are
24. Nucleoid is the region
2. Filament: It is a long stalk like structure that attaches
stamen with
located
helpthe
students
toflower parts, such
as petal.
(a) Genetic material
(b) Proteins
develop the problem(c) Pigments
(d) Nutrients
solving skill
F I g . 4 . 2 5 Longitudinal section of a flower showing all parts
Directions for questions 1 to 20: Fill in the blanks in
each question.
23. Which of the following can change its shape?
25. Bacterial cell wall is made up of
7. The largest cell is ________.
8. Lactobacillus is ________ shaped.
‘Test Supplement
Yourlacks ________.
Reading
S.10
9. Mycoplasma
Anthers
(a) Cellulose
(b) Peptidoglycan
(c) Hemicellulose
(d)
Pectin
Stamen
Chapter 2
2.18
Pollen sacs
26. Match the following
A. Inclusion bodies
(i) Eukaryotic
Filament
MasTeRINg
THe CONCePTs
B. Mesosome
(ii) Protein manufacture
Concepts’
at the
10.
Phosphate granules
are examples for ________.
C.and
Ribosome
(iii) Cell wall formation
end
thefoldings
chapter
Understanding
11.
The of
inner
of the mitochondrialKnowledge
inner
D. Golgi complex
(iv) Nutrient reservoir
membrane
are called
________.
TEST
YOUR
CONCEpTS
for
classroom
12.
Chlorophylls are present in ________.
preparations
1. What are stomata
and
A
B whatCare their
D significance
10. (d)
in a plant?
10. Differentiate
Structure between
of stamen mitosis and meiosis.
(a) (iii)
(ii)
(i)
(iv)
F I g .Differentiate
4 . 2 6 Partsbetween
of stamenbone and cartilage.
11.
13. ________ is known as the energy currency of the
2. Robert
Hooke
(iv)
(iii)
(i) the (ii)
cell.
2. Make a (b)
comparison
between
three types of
11. Scientist
Contribution 12. How epithelial tissues have been classified accord(c) (iii) tissue
(i) based
(iv) on their
(ii) structures.
simple permanent
3. Hypothesis
14.
Detoxification of poisons takes place in ________.
ing to their shape?
Thomas Alva Edison Motion picture camera
(d) (iv)
(iii)
(ii)
(i)
15. Thylakoids of different grana are connected by
4. Observation
3. Differentiate between
xylem and phloem.
Dimitri Ivanovich
Periodic table and13. What is ciliated epithelium, and why are they
27. SelectMendeleev
the wrong statement. periodic law
important in the respiratory tract?
Write the significance of collenchyma in plants?
16. Specialized peroxisomes in plants are 4.
called
(a) Plant
cells Ramanujan
are surrounded
by a living,
Srinivasa
Infinite
series rigid
concepts
are
6.
(d)
________.
14. Make a comparison between tendon and ligament.
outer
layer
called
cell wall.E
2
5. How permanent
tissue
is formed
from
meristeAlbert
Einstein
= mc
further
divided structure
as
17.
Thin thread-like
present inside the
7.
(d)
(b) Plant
cell
wall
is
made
up
of
cellulose.
matic tissue?
Sir Isaac Newton
Universal gravitation
15. Which type of tissue is blood and what is its
nucleus is called ________.
per
(c) Bacterial cell
wall is made Theories
up of peptidoglycan.
8.
(d)Knowledge/
function?
Darwin
6.
What is a Charles
permanent
tissue and how of
it evolution
is
18.
The
membrane
surrounding
vacuole
is
called
Understanding,
and
plasma memJamesprokaryotic
Watson and eukaryotic
DNA structure
9.
(b)
classified?(d) Both
________.
branes are composed of lipids and proteins. 16. Give a note on the structure of neuron.
Mastering
5.
Social sciencethe
________.
8. Give a note
cuticle.
(c) on
Mesosomes
Knowledge
and Understanding
Directions for questions
21 to 40: For each of the fol-
H I N T S A N D E X P L A N AT I O N
Application/Analyze
19.
In plant, reserve food is stored in the form
of
7. What
is phloem
and are
explain
variousbyele- 17. Define pseudopodia.
28.
Adjacenttissue,
plant cells
joineditstogether
________.
ments with their function.
mASTERINg
THE
CONCEpTS
(a) Middle lamella
(b) Plasmodesmata 18. Give a note on axial skeleton.
20. Plant cell wall is made up of ________.
(d) Plasma membrane
19. What are the different types of joints and give an
9. Give 29.
a brief
noteofon
tissue.
lowing questions, four choices have been provided.
example for each?
Which
thexylem
following
is the correct statement?
1. Science
plays alternatives.
a major role in everyday life. It has
to peers may lead to new questions every time
Select
the correct
(a)
Endoplasmic
reticulum
is
the
site
of
protein
made our communication easy, even if we are at
which may in turn lead to another investigation.
21. Site for protein manufacture is
manufacture in bacteria.
far away places. It has also made our transporta3.
Vikram Sarabhai: Father of Indian space
Application
and
(a) Cell
Cytoplasm
tion
easywall
and comfortable. (b)
Through
science, it is (b) The Analysis
membrane-bound inclusion bodies help
Hints and
Explanation for
key questions
programme.
along with
now
possible
to
treat
millions
of
diseases,
thereby
in
the
storage
of
nutrients
in
prokaryotes.
(c) Ribosome
(d) Inclusion bodies
1. You might have
seen that
even after grazing
by 4. It is possible to move the elbow freely. Which
Srinivasa
Ramanujan:
Indian mathematician
increasing the lifespan of people.
highlights
onin this
herbivores, grasses
regenerate
from the remaintypes of joints are present
here that help
who made
major contributions
to number theory,
2. Communicating the results obtained aftering
data
parts. Which
tissue
is
responsible
for
this
and
movement?
the common
infinite series, etc.
analysis to let others know about it is the last step
in it is located?
where
mistakes that
CV Raman: Indian physicist who carried out
a scientific method. The results can be presented as
2. results
Further growth
an onion
after
the
majorofwork
in theroot
field stops
of light
scattering
written or oral reports. Communicating the
students usually
removal of tip portion. Why?
make in the
3. Identify the parts.
Application and Analysis
examination
CTICE QUESTIONS
a n d E x p l a n at i o n
PRACTICE QUESTIONS
1. Albert Einstein
1. Scientists follow a specific pathway for their innovations, which is known as a scientific method. It
involves a series of techniques such as:
• Observation
• Asking questions
• Making hypothesis
• Experimentation
Hypothesis - I - pea seeds do not require
water for germination
~ Hypothesis - II - pea seeds require air for
germination
A III - pea seeds require adequate
~ Hypothesis
amount of both water and air for germination.
• He conducted experiments to prove his
B
hypotheses. He tried to germinate pea seeds in
~
Series Chapter Flow
Class 7
Nutrition in
Plants and
Animals
Respiration in
Plants and Animals
1
5
3
4
2
Transportation in
Plants and Animals
Food and Food
Preservation
Basis of
Classification
Reproduction in Plants
6
7
Our Ecosystem
Class 8
Reproduction in
Animals and Plants
Tissues and Body
Movements
1
3
4
2
Cell—The Basic
Unit of life
Supplement
Reading
Food—
Production and
Management
Classification of
Living Organisms
6
7
Scope of Science
Microorganisms
and Human
Health
5
Ecosystem and
Biodiversity
Series Chapter Flow
xv
Class 9
Diversity in Living
World-Animals
Tissues
1
5
3
4
2
Human Health
and Diseases
Diversity in
Living worldPlants
Cell—Fundamental
Unit of Life
6
Improvement in
Food Resources
Class 10
Reproduction in
Lower Organisms
and plants
Cell Cycle
1
5
3
4
2
Reproduction in
Human Beings
Genetics
10
8
9
Evolution
Ecology
11
Life Processes in
Human Beings-I
Life Processes
in Plants
Cell Division
6
7
Control and
Coordination
Life Processes in
Human Beings-II
This page is intentionally left blank.
Chapter
1
Cell—The basic
Unit of life
ReMeMbeR
Before beginning this chapter, you should be able to:
• Recall the cellular organization in humans
• Remember important cell organelles and their functions
keY IDeas
After completing this chapter, you should be able to:
• Understand the role of cell in maintaining life
• Identify the different cell organelles and their functions
• Differentiate between mitosis and meiosis
1.2
Chapter 1
INTRODUCTION
i
Info Box!
There are more bacterial
cells in human body than
human cells!
If we look around, we see many different objects, some of them are living
and some are non-living. However, both living beings and non-living things
are composed of certain basic chemical elements, such as Carbon, Hydrogen,
Oxygen and Nitrogen. These chemical elements are found in an organized
manner in the form of cells in the living beings, which distinguishes them
from non-living. Cells are the basic structural and functional units of life. A
cell is the smallest individual unit of matter capable of performing all essential
life processes by itself.
Cell—the basic unit of life
The term ‘cell’ is derived from Latin word cellula, meaning ‘little room’. The term cell was
coined by Robert Hooke in 1665. A cell is the smallest building block of life. It is defined as
the basic structural and functional unit of a living organism. A cell is capable of performing
all vital functions to sustain life.
Discovery of Cell
In 1665, Robert Hooke observed the thin slices of cork under a microscope. He noticed several
small compartment-like structures that resembled the structure of a honeycomb.
Fi g . 1 . 1 Microscope used by Robert Hooke
Fi g . 1 . 2 Robert Hooke’s observations of
to make his observations of cells
cellular structure of cork
Cell—The Basic Unit of Life
1.3
Unicellular and Multicellular Organisms
Cell is the basic structural and functional unit of life. All living organisms are
made up of cells. In one case, a single cell may constitute an organism (unicellular) and in other case, an organism may consist of many cells (multicellular).
According to this, organisms can be divided into two types:
i
Info Box!
In 1674, Anton Van Leeuwenhoek observed free
living cells in pond water.
1. Unicellular organisms: Organisms with only one cell, for example,
Amoeba, Chlamydomonas, Paramoecium, bacteria, etc.
Fi g . 1 . 3 Some common unicellular organisms
2. Multicellular organisms: Organisms with many cells, for example,
plants and animals, are called multicellular organisms.
Cell Theory
Cell theory was proposed by Matthias Jakob Schleiden (1838) and Theodor
Schwann (1839) and was later modified by Rudolf Virchow. The two main
postulates are:
i
Info Box!
The number and type of
cells in a given tissue is
called cellularity.
Size and mass of a typical
cell are 10 micrometre and 1
nanogram.
1. All organisms are made up of cells.
2. Cell is the basic structural and functional unit of life.
An important addition to the Cell Theory was made by Rudolph Virchow in 1868. He stated
that new cells arise from pre-existing cells (in Latin: omnis cellula e cellula).
1.4
Chapter 1
Table 1.1 Some famous scientists and their contribution to the field of cell biology
i
Scientist
Contribution
Robert Hooke
Anton Van Leeuwenhoek
Robert Brown
Purkinje
Schleiden, Schwann, Virchow
Camillo Golgi
Discovered cell
Observed first living cell
Discovered cell nucleus
Coined the term ‘protoplasm’
Cell theory
First described Golgi apparatus
Info Box!
Smallest cell: Mycoplasma
Largest cell: Ostrich’s egg
Longest cell: Neuron (in
humans)
Size of Cell
Most cells are minute and are visible only under the microscope. They are
only a few micrometres in diameter. The cells range in size from micrometers
to as long as 1 m. There are some cells which are big enough to be seen with
naked eye. For example, egg of an ostrich is about 15-cm long and 13-cm
wide.
Fi g . 1 . 4 (Left) Microscopic view of cells that are not visible to naked eye (Right) Ostrich eggs in
in nest, Kalahari desert (Africa)
Shape of Cell
i
Info Box!
Naked eye means an
unaided vision, without a
telescope, microscope or
other optical device
The shape of the cells varies according to their function. They may be disclike, polygonal, columnar, cuboid or thread-like. Nerve cells have an elongated
structure and this helps them in conducting impulses quickly. Similarly, there
are cells that have a flexible shape, for example, Amoeba and some blood cells.
The flexibility in Amoeba’s shape helps it to perform various activities, such as
movement, feeding, etc. The change in shape of Amoeba is due to the formation of pseudopodia that are projections on its body.
Cell—The Basic Unit of Life
Red blood cells
(round and biconcave)
White blood cells
(amoeboid)
Columnar epithelial cells
(long and narrow)
Nerve cells
(branched and long)
Fi g . 1 . 5 Different types of cells showing different shapes
Types of Cells
The cells can be divided into two types: prokaryotic and eukaryotic, according to the differences
in their cellular organization. The cells which posses a true nucleus along with membrane-bound
organelles are called eukaryotic cells, example plant cell and animal cell. The cells which do not
possess a well-defined nucleus as well as membrane-bound organelles are called prokaryotic cells,
example bacterial cell.
Prokaryotic Cells
Prokaryotic cells are primitive and lack a true nucleus. Their genetic material is not surrounded
by a nuclear membrane and is confined to a particular region known as nucleoid.
1.5
1.6
Chapter 1
Ribosomes
Fimbriae
Nucleoid
(pili)
Vacuole (DNA) Plasma membrane
Cytoplasm
Cell wall Capsule
Flagella
Fi g . 1 . 6 A prokaryotic cell
Prokaryotic cells are generally smaller than eukaryotic cells. There are four basic shapes for
prokaryotes (bacteria) listed as follows:
1. Coccus 2.
Bacillus 3.
Cocci
Vibrio 4. Spirillum
Bacilli
Spirilla
Coccus Diplococci
Coccobacillus
Tetrad
Others
Bacillus
Sarcina
Corynebacterium
Diplobacilli
Streptococci
Staphylococci
Vibrios
Streptobacilli
Palisades
Spirochete
Fi g . 1 . 7 Illustration of types of bacterial shapes
Though their shapes and sizes vary, all cells possess a common structure. All prokaryotic cells have
major components that are discussed below.
Cell Wall
It forms the outermost layer of the cell. It provides integrity to the cell. It is made up of peptidoglycan, which in turn is made up of carbohydrates. It is absent in Mycoplasma.
Cell—The Basic Unit of Life
1.7
Lipoteichoic acid
Teichoic acid
Peptidoglycan
Cytoplasmic membrane
Membrane protein
Fi g . 1 . 8 Structure of cell wall of bacteria
Plasma Membrane
It lies just inside the cell wall. It isolates the cell’s content from the outside
environment and forms a barrier to substances entering in and out of the cell.
Membranes are semipermeable, meaning they allow only certain substances
to pass through it while preventing others. It is made up of a phospholipid
bilayer.
i
Info Box!
Bacteria are divided into
Gram-positive and Gramnegative depending upon
Gram staining method developed by Christian Gram
Cytoplasm
All of the fluid substance present inside the cell constitutes its cytoplasm. It comprises all kinds of
cell organelles present in a cell, with the exception of no nucleus in a prokaryotic cell.
Mesosomes
These are formed by the plasma membrane extension into the cell. They help in processes, such
as cell wall formation, respiration, etc.
Ribosomes
These are the sites of protein synthesis. Ribosomes are found to be associated with plasma membrane. They are not bound by any membrane system.
1.8
Chapter 1
Large
subunit
mRNA
Small subunit
Fi g . 1 . 9 Diagram showing ribosome structure
Cytoplasmic Inclusions
Inclusion bodies lie free in the cytoplasm. They help in storage of reserve materials, for example,
phosphate granules.
Eukaryotic Cells
All eukaryotic cells possess a true nucleus, that is, their genetic material is surrounded by a nuclear
envelope. All protists, fungi, plants and animals are eukaryotes. They possess membrane bound
organelles, such as endoplasmic reticulum, mitochondria, Golgi bodies, etc.
Nuclear envolope
Nucleolus
Nucleus
Vacuole
Endoplasmic
reticulum
Chloroplast
Cytoplasm
Mitochondrion
Golgi apparatus
Cell wall
Cell Membrane
Fi g . 1 . 1 0 A typical plant (eukaryotic) cell
All eukaryotic cells typically have:
Cell Wall
Plant cells are surrounded by a non-living, rigid, permeable outer layer known as a cell wall.
It provides structural integrity and protection to the cell. It is made up of cellulose. Cell walls
of adjacent cells are joined together by a jelly-like substance called middle lamella.
Cell—The Basic Unit of Life
Cell Membrane
It is made up of proteins and lipids. Cell membrane is semi-permeable which means that it allows
entry and exit of only some materials.
Extracellular fluid
Transmembrane
glycoprotein
Carbohydrates
Pore
Glycolipid
Cholesterol
Peripheral Transmembrane
protein
protein
Channel protein
Cytoplasm
Fi g . 1 . 1 1 Plasma membrane structure
Protoplasm
The living material comprising cytoplasm, nucleus and other organelles is called protoplasm.
Cytoplasm
Fluid content inside the cell membrane. Contains many membrane-bound organelles. These are
discussed in detail in the following section.
Cell wall
Plasma membrane
Cytoplasm
Prokaryotic
Cell
Mesosomes
Ribosomes
Nucleus
Inclusion bodies
Cell wall
Plant cell
Plasma membrane
Cytoplasm
Eukaryotic
Animal cell
Nucleus
Plasma membrane
Cytoplasm
Fi g . 1 . 1 2 Cellular organization in prokaryotes and eukaryotes
1.9
1.10
Chapter 1
Table 1.2 Differences between prokaryotic and eukaryotic cell
Prokaryotic cell
Eukaryotic cell
Size generally small (1–10 mm)
True nucleus is absent
Contains single chromosome
Membrane-bound cell organelles absent, such as
endoplasmic reticulum, Golgi complex, etc.
Size generally large (5–100 mm)
Nucleus is present
Contains more than one chromosome
Membrane-bound cell organelles present
Cell Organelles
An organelle is a unit inside the cell that performs a special function. The various functions performed by a cell are actually divided among the organelles, that is, there is a division of labour
inside the cell in eukaryotic cells. This division of labour is absent in prokaryotic cells. For
example, energy production is performed by mitochondria, photosynthesis by plastids, etc. The
various cytoplasmic organelles are given below:
Endoplasmic Reticulum
It is a large network or reticulum of membrane-bound tiny tubular structures that start at the
nuclear membrane and extend into the cytoplasm. They are mainly involved with the synthesis,
folding, modification and transport of proteins.
Endoplasmic reticulum is of two types:
1. R
ough Endoplasmic Reticulum (RER): which possesses ribosomes on its surface and
helps in protein synthesis.
2. S
mooth Endoplasmic Reticulum (SER): which lacks ribosomes on its surface.
They are a major site for lipid synthesis and also involved in the detoxification of
poisons.
Nucleus
Rough ER
Smooth ER
Ribosomes
Fi g . 1 . 1 3 Rough ER and Smooth ER
Cell—The Basic Unit of Life
1.11
Ribosomes
It consists of dense and spherical particles which are present in both
prokaryotic and eukaryotic cells. These are the sites of protein manufacture. They are found either free in cytoplasm or attached with
RER. These are not bound by any membrane and are complex of
ribonucleic acid (RNA) and proteins.
Golgi Apparatus
It was first described by Camillo Golgi in 1898. It consists of a system of many, flat disc-shaped sacs called cisternae, which are arranged
parallel to each other. Its functions include packaging, storing and
dispatching of various products received from endoplasmic reticulum.
It remains in close association with endoplasmic reticulum. It is
involved in synthesis of complex sugars and lysosome.
Lysosomes
These are composed of tiny spherical structures surrounded by a
Fi g . 1 . 1 4 Golgi Apparatus
single membrane. They contain many digestive enzymes that are
manufactured in RER. Lysosomes are known as waste disposal system of the cell as they help in cleaning the cell by removing the worn out or damaged cellular
organelles. They are also called suicide bags of cells as they can digest their own cell, if anything
happens to the cell structure or if the cell gets damaged.
Membrane
Lipid layer
Glycosylated
mambrane
transport
proteins
Hydrolytic
enzyme
mixture
Fi g . 1 . 1 5 Lysosome structure
Mitochondria
They are referred to as the powerhouses of the cell. They are the main sites for energy production. They produce energy in the form of adenosine triphosphate (ATP). ATP is known as
energy currency of the cell. Number of mitochondria per cell vary according to the physiological
activity of the cell.
Structure of a typical mitochondrion is characterized by the following features.
••
••
••
••
••
It is surrounded by a double membrane covering.
Its outer membrane is porous and inner membrane is deeply folded.
The foldings of inner membrane are called cristae which increase the surface area.
The compartment enclosed by inner membrane is called matrix.
Mitochondrion possesses its own DNA (single circular DNA) and ribosomes.
1.12
Chapter 1
DNA
Matrix
Ribosomes
F0, F1
Complexes
Inner
Outer
Membrane Membrane
Cristae Junction
Intermembrane
Space
Fi g . 1 . 1 6 Structure of mitochondria
i
Info Box!
Green chilly is converted
into red chilly due to conversion of chloroplast into
chromoplast.
Plastids
Plastids are present in most plant cells and are absent in animal cells. Like mitochondria, plastids contain their own DNA and ribosomes. Plastids are of three
types as detailed below:
Plastids
Chromoplasts
Chloroplasts
Leucoplasts
Yellow or
orange
pigment
Green
pigment
Colorless
Aleuroplasts
Elaioplasts
Amyloplasts
Store protein
Store oil
Store carbohydrate
Fi g . 1 . 1 7 Division of plastids on the basis of presence or absence of pigments
1. Chromoplasts: Coloured plastids in which chlorophyll is absent and contain yellow or orange
pigment. They are found in fruits, flowers, etc.
2. Chloroplasts: Consist of a green pigment called chlorophyll and it mainly functions in
photosynthesis. Chloroplast is also known as kitchen of the cell.
3. Leucoplasts: They are white or colourless and mainly function in storage. Depending
upon the storing material, leucoplasts are of three types; Aleuroplast (store protein), elaioplast (stores oil), amyloplast (stores carbohydrate).
Structure of Chloroplasts
It is surrounded by a double membrane covering. It consists of many membrane-bound flat discs
called thylakoids which has chlorophyll. Thylakoids are arranged in stacks called grana. The
matrix found inside the chloroplast is called stroma. Thylakoids of different grana are connected
by stromal lamellae
Cell—The Basic Unit of Life
Outer membrane
Inner membrane
DNA
Stroma
Plastoglobulus
Ribosome
Thylakoid
Starch grain
Fi g . 1 . 1 8 Structure of choloroplast
Vacuoles
These are membrane bound spaces seen in the cytoplasm of mainly plant and fungal cells. These
are the storage sacs that store proteins, amino acids, water and other nutrients. They can occupy
up to 90% of the cell volume in plant cells. In animal cells, vacuoles are either very small or
absent. It is surrounded by a single membrane called tonoplast. The substance present inside the
vacuole is called cell sap. It provides turgidity and rigidity to the plant cell.
Microbodies
Microbodies are a kind of organelles present in plants, animals and protozoa. They include peroxisomes, glyoxysomes, glycosomes and hydrogenosomes.
1. Peroxisomes: Present in cytoplasm and mainly function in the detoxification of toxic
substances.
2. Glyoxysomes: Specialized peroxisomes in plants.
3. Glycosomes: Specialized peroxisomes present in protists.
4. Hydrogenosomes: Found in anaerobic eukaryotes.
Centrosomes
They are only found in animal cells. They are not bounded by a membrane and consist of two
centrioles. Centrosomes help in cell division.
Nucleus
It was first described by Robert Brown in the year 1831. It is a large, spherical, centrally placed
organelle found in eukaryotic cells which is the central controlling unit of all the activities of a
cell.
Structure of nucleus
It is surrounded by a double membrane called nuclear envelope or nuclear membrane. Nuclear
envelope contains many pores called nuclear pores. Nuclear pores allow transport of materials
across nucleus that is, from nucleus to cytoplasm and from cytoplasm to nucleus. Liquid substance present inside the nucleus is called nucleoplasm. It contains nucleolus and chromatin
material.
1.13
1.14
Chapter 1
Anatomy of the nucleus
and endoplasmic reticulum
Nuclear envelope
Nucleus
Nucleolus
Chromatin
Nuclear pore
Rough endoplasmic
reticulum
Smooth endoplasmic
reticulum
Ribosomes
Fi g . 1 . 1 9 Nucleus
Nucleolus is the place where ribosomes are synthesized, it is rich in protein and RNA molecules.
Chromatin material consists of thin, thread-like, entangled structure composed of deoxy-ribonucleic acid (DNA) and proteins. At the time of cell division, chromatin condenses to form rodshaped chromosomes.
DNA stores information necessary for the inheritance of characters from parents to offsprings.
Functional segments of DNA are called genes.
Nucleus is the control centre of the cell as it controls the metabolic activities of the cell. Usually
there is only one nucleus per cell, but there are exceptions where more than one nucleus is present, for example, Paramoecium. Some mature cells even lack nucleus, for example, RBCs.
Cell
Nucleus
Chromosome
P arm
Centromere
DNA
Q arm
Sugar-phosphate
backbone
Sister
chromatids
Gene
Cytosine
Guanine
Adenine
Thymine
Fi g . 1 . 2 0 Organization and compaction of DNA inside nucleus
Cell—The Basic Unit of Life
Comparative Study of Animal and Plant Cells
Animal and plant cells show considerable variations in their structure. Plant cells are surrounded
by an outer cell wall, whereas cell wall is absent in animal cells. Similarly, plastids and large central
vacuoles are present in plant cells but are absent in animal cells.
Table 1.3
Differences between animal and plant cell
Animal cell
Plant cell
Usually smaller in size and oval in shape
Comparatively larger in size and rectangular in
shape
Cell wall is absent
Present (cellulose)
Vacuoles are either absent or very small
Large central vacuole
Golgi complex is well developed and is
present near the nucleus
Components of Golgi complex in plant cells are
called dictyosomes
Centrosome and centrioles are present
Absent
Plastids are absent
Present
Reserve food is stored in the form of
glycogen
Stored in the form of starch or oil
Rouch
endoplasmic
reticulum
Smooth
endoplasmic
reticulum
Golgi apparatus
Chloroplast
Nucleus
Ribosomes
Vacuole
Plasma
membrane
Microbody
Cell wall
Mitochondria
Fi g . 1 . 2 1 A typical plant cell showing all major organelles
1.15
1.16
Chapter 1
Rough endoplasmic reticulum (ER)
Smooth ER
Golgi apparatus
Nuclear pore
Nucleus
Vesicles
Nuclear
envelope
Centrioles
Microtubules
Microfilaments
Mitochondrion
Ribosomes
Lysosome
Plasma membrane
Fi g . 1 . 2 2 A typical animal cell showing all major organelles
Various Organelles and their Role in Cell
Functions of all the cell organelles are collaborated in the table below.
Table 1.4 Functions of different organelles in a cell
Organelle
Functions
Endoplasmic reticulum
Ribosome
Golgi complex
Protein and lipid synthesis
Protein manufacture
Packaging, storing and dispatching of materials received from the
endoplasmic reticulum
Waste disposal system of the cell
Storage sac, provides rigidity and turgidity to the plant cell
Power house of the cell
Photosynthesis
Cell division
Control centre of the cell, contains chromosomes
Quick Recap
Lysosome
Vacuole
Mitochondria
Chloroplast
Centrosome
Nucleus
1. The size and shape of cell vary. Justify the statement.
The size and shape of cells vary according to their function. For example, nerve cells have an elongated
structure that helps them to conduct nerve impulses quickly.
2. List out the various shapes of bacteria and give examples for each.
There are basically four different shapes for bacteria:
(i) Rod-shaped or bacillus, Lactobacillus.
(ii) Spherical-shaped or coccus bacteria, Staphylococcus.
(iii) Spiral-shaped bacteria, for example, Treponema.
(iv) Comma-shaped bacteria, for example, Vibrio cholerae.
1.17
3. What are inclusion bodies?
Inclusion bodies are structures that lie free in the cytoplasm and help in storage of reserve materials, for
example, phosphate granules, glycogen granules, etc.
4. Differentiate between rough and smooth endoplasmic reticulum.
Rough endoplasmic reticulum
Smooth endoplasmic reticulum
Looks rough under the microscope
Ribosomes are present on the surface
Involved in protein synthesis
Looks smooth under the microscope
Ribosomes are absent
Major site for lipid synthesis and is also
involved in the detoxification of poisons
5. Which organelle is the waste disposal system of the cell and why is it called so?
Lysosome is known as the waste disposal system of the cell. Lysosome encloses many digestive enzymes
and it helps in cleaning the cell by removing the worn out or damaged cellular organelles. It also helps in
destroying foreign materials such as bacteria and virus entering the cell. Hence, lysosome is also known
as the waste disposal system of the cell.
6. Give a note on the structure of mitochondria.
Mitochondria are surrounded by a double membrane covering. The outer membrane is porous and the
inner membrane is deeply folded. The folding seen inside the inner membrane is called crista and it helps
in increasing the surface area. The compartment enclosed by inner membrane is called matrix. Mitochondria possess their own DNA (single circular DNA) and ribosomes.
7. What are leucoplasts and what are their various types?
eucoplasts are white or colourless plastids that mainly function in storage. Depending upon the storage
L
material, leucoplasts are of three types:
Aleuroplasts: Store protein
Elaioplasts: Store oil
Amyloplasts: Store carbohydrates
8. What are the main functions of nucleus?
ucleus is the control centre of the cell, and controls the metabolic activities of the cell. Nucleus contains the
N
genetic material, thus stores information necessary for the inheritance of characters from parents to offsprings.
It also plays a major role in cellular reproduction, that is, the formation of new cells from the parent cell.
Cell Division
The process in which a cell divides into two daughter cells is called cell division. In single celled
organisms, one cell division results in the formation of two new organisms, for example, Amoeba,
bacteria, etc. Cell division in prokaryotes is much simpler as compared to that in eukaryotes.
Cell Division in Prokaryotes
The common type of cell division seen in prokaryotes is binary fission. The fully grown parent
divides into two halves resulting in two new cells.
Quick Recap
Cell—The Basic Unit of Life
1.18
Chapter 1
Two offsprings
Parent
Fi g . 1 . 2 3 Binary fission
Significance of Cell Division
Reproduction: A cell must divide in order to reproduce. Hence, cell division is responsible for
continuity of life.
Replacement of cells: All cells have a limited lifespan. They die after completing their lifetime.
New cells are needed to replenish this loss. Hence, cell division helps in replacement of dead cells
by producing new cells.
Growth: We observe that an infant grows into an adult, a small seed grows into a big tree, etc.
These changes are possible only when the number of cell increases in order to increase the size of
the organism. Hence, cell division enables the living organisms to grow.
Cell Division in Eukaryotes
Cell division in eukaryotes is more complex than in prokaryotes and involves two processes:
1. Karyokinesis: Division of nucleus
2. Cytokinesis: Division of cytoplasm
There are two different types of cell division:
1. Mitosis
2. Meiosis
Mitosis
A kind of cell division that results in the formation of daughter cells that are genetically identical
to the parent cell. Daughter cells produced by mitosis possess the same number of chromosomes
as that of parent cell. Mitosis can be divided into four stages:
1.
2.
3.
4.
Prophase
Metaphase
Anaphase
Telophase
Cell—The Basic Unit of Life
Each chromosome makes
an identical copy of itself.
The chromosomes line up
across the centre of the cell.
One complete set of
chromosomes moves
to each end of the cell.
The cell starts to divide in two and split
apart. Each new cell is a daughter cell.
The daughter cells contain identical
chromosomes in their nuclei and carry
identical genes to the parent cell.
1.19
Fi g . 1 . 2 4 Phases of mitosis
In animals, mitosis occur generally only in diploid somatic cells, whereas in
some lower plants, mitosis can occur in haploid cells also. A cell that contains
two sets of chromosomes (two copies of the same chromosome) is called diploid cell, whereas a cell with only one set of chromosome is called haploid
cell. Mitosis occurs as a part of normal cell growth and to replace worn out
cells.
i
Info Box!
A somatic cell is any cell
other than reproductive cells
or germ cells.
Meiosis
Meiotic cell division occurs during sexual reproduction leading to gamete formation. The daughter cells formed possess half the number of chromosomes than the parent cell. Meiosis involves
two sequential cycles of divisions:
1. Meiosis I
2. Meiosis II
Both meiosis I and II can be again subdivided into four stages as given below.
1.20
Chapter 1
Meiosis I
Meiosis II
Prophase I
Metaphase I
Anaphase I
Telophase I
Prophase II
Metaphase II
Anaphase II
Telophase II
Mitosis
Meiosis
Diploid
Diploid
46
46
23
23
46
46
Diploid
23
23
23
23
Haploid
Fi g . 1 . 2 5 Diagrammatic representation of Mitosis and Meiosis
Main differences between mitosis and meiosis are given in the table below.
Quick Recap
Table 1.5
Differences between Mitosis and Meiosis
Mitosis
Meiosis
Occurs generally in somatic cells
During normal growth of cell
Chromosome number remains the same
Two daughter cells are formed
Occurs in germ cells
During gamete formation
Chromosome number reduces to half
Four daughter cells are formed
1. Who discovered cell and how?
obert Hooke in 1665 discovered cell while he was observing a thin slice of cork under a microscope.
R
He observed a structure similar to honeycomb and named this structure ‘cell’.
2. Give a brief note on the differences between unicellular and multicellular organisms.
Unicellular organisms
Multicellular organisms
Composed of only one cell
Single cell performs the entire functions
For example, Amoeba and bacteria
Contain many cells
Various functions are performed by many cells
For example, plants and animals
3. Give a note on binary fission.
inary fission is a kind of cell division seen in prokaryotes. The fully grown parent cells divide into two
B
halves producing two new cells. It involves division of nucleus followed by division of cytoplasm, ultimately resulting in two daughter cells.
1.21
4. Define mitosis and write its significance.
itosis is the kind of cell division that results in the formation of two daughter cells that are genetically
M
identical to the parent cell. Daughter cells possess the same number of chromosomes as of parent cell.
Mitosis occurs as a part of normal cell growth and to replace worn out cells.
5. Give a note on diploid cell and haploid cell with an example.
cell that contains two sets of chromosomes, that is, two copies of the same chromosome, one from each
A
parent is called diploid cell. Haploid cell contains only one set of chromosomes, for example in human
diploid cells (any cell other than gametes), there are 46 chromosomes whereas human gamete is haploid
with 23 chromosomes.
POINTS TO REMEMBER
•• A cell is the smallest individual unit of matter capable of performing all essential life processes
by itself.
•• Cell theory was proposed by Matthias Jakob Schleiden (1838) and Theodor Schwann (1839)
•• Rudolph Virchow stated that new cells arise from pre-existing cells
•• Prokaryotic cells are primitive type of cells which lack a true nucleus and membrane bound
organelles.
•• Eukaryotic cells possess a true nucleus, that is, their genetic material is surrounded by a
nuclear envelope and have membrane bound organelles, example, plant cell.
•• The process in which a cell divides into two daughter cells is called cell division
•• Cell division is required for growth, reproduction and repair.
•• Mitosis is that type of cell division that results in the formation of daughter cells that are
genetically identical to the parent cell.
•• Meiosis is that type of cell division which occurs during sexual reproduction leading to
gamete formation.
Quick Recap
Cell—The Basic Unit of Life
1.22
Chapter 1
TEST YOUR CONCEPTS
Directions for questions 1 to 20: Fill in the blanks in
each question.
1. The first living cell was discovered by ________
2. ________ is the basic structural and functional
unit of life.
3. Take the odd one out.
Amoeba, Bacteria, Plant, Honeybee.
4. The concept ‘Omnis cellula e cellula’ was put forward by ________.
5. The term ‘protoplasm’ was coined by ________.
6. The smallest cell is ________.
7. The largest cell is ________.
8. Lactobacillus is ________ shaped.
9. Mycoplasma lacks ________.
10. Phosphate granules are examples for ________.
11. The inner foldings of the mitochondrial inner
membrane are called ________.
12. Chlorophylls are present in ________.
PRACTICE QUESTIONS
13. ________ is known as the energy currency of the
cell.
14. Detoxification of poisons takes place in ________.
15. Thylakoids of different grana are connected by
________.
16. Specialized peroxisomes in plants are called
________.
17. Thin thread-like structure present inside the
nucleus is called ________.
18. The membrane surrounding vacuole is called
________.
19. In plant, reserve food is stored in the form of
________.
20. Plant cell wall is made up of ________.
22. The longest cell is
(a) Mycoplasma
(c) PPLO
(b) Neuron
(d) Ostrich egg
23. Which of the following can change its shape?
(i) Amoeba
(ii) Neuron
(iii) WBC(iv) RBC
(a) (i) only
(b) (i) and (ii)
(c) (i) and (iii)
(d) (i), (ii), (iv)
24. Nucleoid is the region where ________ is/are
located
(a) Genetic material
(b) Proteins
(c) Pigments (d) Nutrients
25. Bacterial cell wall is made up of
(a) Cellulose
(b) Peptidoglycan
(c) Hemicellulose (d) Pectin
26. Match the following
A. Inclusion bodies
B. Mesosome
C. Ribosome
D. Golgi complex
(a)
(b)
(c)
(d)
A
(iii)
(iv)
(iii)
(iv)
B
(ii)
(iii)
(i)
(iii)
C
(i)
(i)
(iv)
(ii)
(i)
(ii)
(iii)
(iv)
Eukaryotic
Protein manufacture
Cell wall formation
Nutrient reservoir
D
(iv)
(ii)
(ii)
(i)
27. Select the wrong statement.
(a)Plant cells are surrounded by a living, rigid
outer layer called cell wall.
(b) Plant cell wall is made up of cellulose.
(c)Bacterial cell wall is made up of peptidoglycan.
(d)Both prokaryotic and eukaryotic plasma membranes are composed of lipids and proteins.
28. Adjacent plant cells are joined together by
Directions for questions 21 to 40: For each of the following questions, four choices have been provided.
Select the correct alternatives.
(a) Middle lamella
(b) Plasmodesmata
(c) Mesosomes
(d) Plasma membrane
21. Site for protein manufacture is
29. Which of the following is the correct statement?
(a) Cell wall
(b) Cytoplasm
(c) Ribosome
(d) Inclusion bodies
(a)Endoplasmic reticulum is the site of protein
manufacture in bacteria.
Cell—The Basic Unit of Life
30. Which one of the followings are included in
protoplasm?
(i) Nucleus (ii) Cytoplasm
(iii) Organelles
(iv) Nucleoplasm
(a) (i) and (ii)
(b) (i), (ii), (iii)
(c) (ii) only
(d) (i), (ii), (iii), (iv)
31. Ribosomes are composed of ________ and
________
(a) Lipids, proteins
(b) RNA, proteins
(c) DNA, proteins
(d) Proteins only
32. The organelle that is involved in the formation of
lysosome is
(a) Golgi apparatus
(b) Mitochondria
(c) Endoplasmic reticulum (d) Vacuole
33. Which of the following organelles are covered by
single membrane?
(a) Ribosome and lysosome
(b) Lysosome and nucleus
(c) Ribosome and vacuole
(d) Lysosome and vacuole
34. Select the correct statements.
A.Ribosomes are covered by a double-layered
membrane.
B.
Ribosomes are composed of RNA and
proteins.
C. Chlorophyll is absent in chromoplast.
D. Elaioplasts store protein.
(a) A and D
(b) B and C
(c) C and D
(d) B and D
35. Which of the following organelles possess their
own DNA and ribosomes?
(a) Mitochondria and plastids
(b) Plastids and endoplasmic reticulum
(c) Mitochondria and Golgi complex
(d) Golgi complex and endoplasmic reticulum
36. Energy is produced in the form of _________
(a) ATP(b) GTP
(c) AMP(d) ADP
37. Which of the following statement is wrong?
(a)Vacuoles are either absent or small in animal
cells.
(b) Centrosomes are absent in animal cells.
(c) Centrosomes are absent in plant cells.
(d) Centrosomes help in cell division.
38. Glycosomes are specialized peroxisomes found in
(a) Animals (b) Plants
(c) Protists(d) Bacteria
39. Functional segments of DNA are called
(a) Genes(b) Chromosomes
(c) Chromatin
(d) Centrosome
40. Which of the following cell lacks nucleus?
(a) Mature RBC
(b) Mature WBC
(c) Neutrophils
(d) Paramoecium
MASTERING THE CONCEPTS
Knowledge and Understanding
1. Who postulated cell theory and what are the main
postulates?
4. Differentiate between prokaryotic and eukaryotic
cells.
2. How does Staphylococcus differ from Lactobacillus in
shape?
5. Unlike prokaryotes, all eukaryotic cells are not
identical. Justify the statement.
3. What are mesosomes and write their significance
in the cells?
6. Why plasma cell membranes are said to be semipermeable in nature?
PRACTICE QUESTIONS
(b)The membrane-bound inclusion bodies help
in the storage of nutrients in prokaryotes.
(c)
The living material inside the cell is called
protoplasm.
(d)Mesosome is the cell wall extension that helps
in photosynthesis.
1.23
1.24
Chapter 1
7. Explain the structure of chloroplast.
8. Make a comparison between the three types of
leucoplasts.
9. Differentiate between nucleolus and nucleoid.
10. Which organelles are known as semi-autonomous
organelles and why are they called so?
12. Which organelle is known as ‘power house’ of the
cell and why is it called so?
13. What are vacuoles and what is their role in a cell?
14. Explain the structure of cell nucleus.
15. Differentiate between animal cell and plant cell
based on structure.
11. Give a note on Golgi apparatus and its functions.
Application and Analysis
1. Complete the table given below:
Structure
(a) ________
Ribosome
(c) ________
(d) Plasma
membrane
(b)
(e)
________
(f)
________
Features
Plasma membrane extension
Site of ________
Joins adjacent plant cells
Made up of ________ and
________
Living material inside the
cell
Fluid content inside the cell
membrane
PRACTICE QUESTIONS
2. Why Golgi apparatus is seen associated with endoplasmic reticulum inside the cell?
3. Why lysosomes are also called ‘suicide bags’ of
cells?
4. Animal cells differ from plant cells in a number of
ways. What is one specific characteristic that makes
their mode of nutrition significantly different?
5. Both bacteria and plants contain cell walls yet they
are entirely different from each other. Justify.
6. A eukaryotic cell has mitochondria in their cytoplasm which are specially organized organelles that
perform respiration. Whereas prokaryotic cells lack
mitochondria yet they perform respiration. How?
7. There are two substances, namely ‘A’ and ‘B’ which
are present outside a cell. Substance ‘A’ is able to
pass through the cell and ‘B’ is not able to do so.
How can you justify this selective movement of
substances in and out of a cell?
8. After one round of division, a cell receives half the
number of chromosomes as in the parent cell. What
can be inferred about the nature of the parent cell?
Cell—The Basic Unit of Life
1.25
1. Anton Van Leeuwenhoek
21. (c)
2. Cell
22. (b)
3. Bacteria (all others are eukaryotes)
23. (c)
4. Rudolf Virchow
24. (a)
5. Purkinje
25. (b)
6. Mycoplasma
26. (d)
7. Ostrich egg
27. (a)
8. Rod
28. (a)
9. Cell wall
29. (c)
10. Inclusion bodies
30. (d)
11. Cristae
31. (b)
12. Thylakoids
32. (a)
13. ATP
33. (d)
14. Smooth endoplasmic reticulum
34. (b)
15. Stroma lamellae
35. (a)
16. Glyoxysomes
36. (a)
17. Chromatin material
37. (b)
18. Tonoplast
38. (c)
19. Starch
39. (a)
20. Cellulose
40. (a)
MASTERING THE CONCEPTS
Knowledge and Understanding
1. Cell theory was proposed by Matthias Jakob
Schleiden (1838) and Theodor Schwann (1839)
and was later modified by Rudolf Virchow. The
main postulates are:
•• All organisms are made up of cells.
•• Cell is the basic structural and functional unit
of life.
•• All cells arise from pre-existing cells only (Omnis
cellula e cellula)
2. Staphylococcus is spherical in shape whereas
Lactobacillus is rod shaped.
3. Mesosomes are the structures seen in prokaryotes, which are formed by the plasma membrane
extension into the cell. Mesosomes help in cellular
activities, such as cell wall formation, respiration,
etc.
4. Prokaryotic cell
Size generally small
(1–10 mm)
Nucleus is absent
Contains single
chromosome
Membrane-bound
cell organelles, such as
endoplasmic reticulum,
Golgi complex, etc., are
present
Eukaryotic cell
Size generally large
(5–100 mm)
Nucleus is present
Contains more than
one chromosome
Membrane-bound
cell organelles are
present
H i n t s a n d E x p l a n at i o n
TEST YOUR CONCEPTS
1.26
Chapter 1
5. Eukaryotic cells include protista, plants, animals,
fungi, etc. All of them show considerable difference in their structure and organization. For
example, plant cells are surrounded by an outer
cell wall, whereas cell wall is absent in animal cells.
Similarly, plastids and large central vacuoles are
present in plant cells but are absent in animal cells,
and if vacuoles are present in animal cells, they will
be very small.
6. Plasma cell membranes are made up of proteins
and lipids. They are said to be semi-permeable
membranes, as they allow entry and exit of only
some materials and prevent others.
H i n t s a n d E x p l a n at i o n
7. Chloroplast is the plastid that contains a green
pigment called chlorophyll. It mainly functions
in photosynthesis. Chloroplast is surrounded by a
double membrane covering, an outer membrane
and an inner membrane. It consists of many membrane-bound flat discs called thylakoids that have
chlorophyll molecules. Thylakoids are arranged in
stacks called grana. The matrix found inside the
chloroplast is called stroma. Thylakoids of different
grana are connected by stromal lamellae.
Outer membrane
Inner membrane
12. Mitochondria are known as powerhouses of the
cell as they are the main sites for energy production. Mitochondria produce energy required for
various chemical activities in the form of adenosine triphosphate (ATP). ATP is known as energy
currency of the cell. The number of mitochondria
per cell vary according to the physiological activity
of the cell.
13. Vacuoles are membrane-bound spaces seen in the
cytoplasm. They are the storage sacs that store
DNA
proteins, amino acids, water and other nutrients.
Stroma
In plant cells, vacuoles can occupy up to 90%
Plastoglobulus
of the volume, whereas in animal cells, vacuoles
are either very small or absent. Vacuoles are surRibosome
rounded by a single membrane called tonoplast
Thylakoid
and the substance inside a vacuole is called cell
sap. Vacuoles provide turgidity and rigidity to the
Starch
plant cell.
grain
Internal structure of chloroplast
8. Leucoplasts are colourless plastids that mainly
function in storage. Leucoplasts are of three types,
such as aleuroplasts, elaioplasts and amyloplasts.
Aleuroplasts store protein, elaioplasts store oil,
whereas amyloplasts store carbohydrates (starch).
9. Nucleolus
Present in eukaryotes
Region inside the
nucleus that is rich in
RNA and protein
10. Mitochondria and plastids are known as semiautonomous organelles as they contain their own
DNA and ribosomes. Both of them can synthesize
some of the proteins required for the function on
their own.
11. Golgi apparatus comprises a system of many, flat
disc-shaped sacs called cisternae. They are arranged
parallel to each other. Major functions of Golgi
apparatus include packaging, storing and dispatching of various products received from the endoplasmic reticulum. For this reason, Golgi apparatus remains in close association with endoplasmic
reticulum. Golgi apparatus is also involved in synthesis of complex sugars and lysosomes.
Nucleoid
Present in prokaryotes
Region in the
cytoplasm where
genetic material is
present
14. Nucleus is the large, spherical, centrally placed
organelle found in eukaryotic cells. It is surrounded by a double membrane called nuclear
envelope. Nuclear envelope contains many pores
called nuclear pores, which allow the transport of
materials across the nucleus. The liquid substance
present inside the nucleus is called nucleoplasm,
which contains nucleolus and chromatin material.
Nucleolus is the region, which is rich in RNA
and protein and not enclosed by a membrane.
Chromatin is the thread-like structure composed
of DNA and proteins. DNA stores information
necessary for the inheritance of characters from
parents to offsprings.
Cell—The Basic Unit of Life
Nucleus
Nuclear envelope
Nucleolus
Chromatin
Nuclear pore
Rough
endoplasmic
reticulum
Smooth
endoplasmic
reticulum
Ribosomes
Nucleus
15. Animal cell
Usually smaller in size
and oval in shape
Cell wall is absent
Vacuoles are either
absent or very small
Golgi complex are
well developed and
present near nucleus
Centrosome and
centrioles are present
Plastids are absent
1.27
Plant cell
Comparatively larger
in size and rectangular
in shape
Present (cellulose)
Large central vacuole
Components of Golgi
complex in plant cells
are called dictyosomes
Absent
Present
1. Structure
Features
(a) Mesosome
Plasma membrane
extension
(b) Ribosome
Site of protein
manufacture
(c) Middle lamella Joins adjacent plant cells
(d) Plasma
membrane
Made up of lipids and
proteins
(e) Protoplasm
Living material inside the
cell
(f)
Fluid content surrounded
by the cell membrane
Cytoplasm
2. Main functions of Golgi apparatus include packaging, storing and dispatch of various products
received from the endoplasmic reticulum. It modifies the proteins and lipids received from the endoplasmic reticulum and also directs these products
to various targets. For this reason, Golgi apparatus
remains in close association with the endoplasmic
reticulum.
3. Lysosomes are tiny, spherical structures that contain many digestive enzymes. If any kind of disturbance is caused to the cell structure and its organization, lysosomes burst releasing their enzymes.
These enzymes are capable of digesting their own
cell. Therefore, lysosomes are also known as ‘suicide bags’ of cells.
4. Plant cells contain a specialized organelle, chloroplast which contains chlorophyll, while animal
cells do not contain chloroplast. Plants are capable
of synthesizing their own food with the help of
chloroplast in the presence of sunlight and water,
whereas animal cell is not able to do so. Hence,
plants show autotrophic mode of nutrition and
animals show heterotrophic mode of nutrition.
5. Bacterial cell walls are different from the cell walls
of plants in terms of composition. Major component of bacterial cell wall is peptidoglycan while the
major component of plant cell walls is cellulose.
6. The plasma membranes of prokaryotic cells (bacterial cells) have special ingrowths that are called
mesosomes which are the sites for respiration.
Therefore, a prokaryotic cell is able to carry out the
process of respiration even without mitochondria.
7. Cells are surrounded by a selectively permeable
membrane called plasma membrane. This membrane is designed such that it allows certain specific
molecules to pass through it while not allowing
certain molecules to do so. Hence, this selective
nature of plasma membrane guides the entry and
exit of substances around the cell.
8. Since the number of chromosomes is reduced to
half in the process of division, it can be inferred
that the division is through meiosis. We know that
meiosis occurs only in germ cells. Hence, the parent cell is a germ cell.
H i n t s a n d E x p l a n at i o n
Application and Analysis
This page is intentionally left blank.
Chapter
2
Tissues and
Body Movements
ReMeMBeR
Before beginning this chapter, you should be able to:
• Recall the basic features of a cell
• Remember the meaning and organization of tissue
key IDeas
After completing this chapter, you should be able to:
• Understand different types and functions of plant tissues
• Understand different types and functions of animal tissues
• Describe human skeletal system
2.2
Chapter 2
INTRODUCTION
All living organisms are made up of cells, and the living world comprises both unicellular and
multicellular organisms. In unicellular organisms, a single cell performs all functions or activities needed for the survival and in multicellular organisms, the work is divided among group of
cells, i.e., there is a division of labour. Tissue can be defined as a group of cells either similar or
dissimilar that perform a specific function, for example, muscular tissue in humans is involved in
movement or locomotion, and blood connective tissue helps in transport of respiratory gases and
nutrients.
Tissue
Dead
Living
Meristematic
tissues
Sclerenchyma
Phloem fibres
Phloem
(Sieve tubes,
Xylem vessel,
companion cells,
tracheids, fibres
Xylem phloem parenchyma)
parenchyma
Collenchyma
Parenchyma
F i g . 2 . 1 Classification of tissues—in general
Plant Tissue
Plant body is composed of different types of tissues, like meristematic tissues, vascular tissues, etc.
Unlike animals, plant body is abundant in dead supportive tissues. Plants are adapted for a sedentary existence as they do not move. Because of this reason, the
main requirement is structural support which can be provided by
Apical meristem
dead tissues with least maintenance.
In plant body, the growth is not uniform, that is, their
growth is confined to particular regions. Plant tissues according
to their dividing abilities can be divided into two:
Intercalary meristem
1. Meristematic tissue
2. Permanent tissue
Meristematic Tissue
Lateral meristem
F i g . 2 . 2 Location of different types of
meristem on a plant
The plant tissue that can be divided throughout its life is called
meristematic tissue. Meristematic tissues can be again divided
according to their position as:
1. A
pical meristem: Seen at the growing tips of roots and
shoots and helps in increasing length of root and stem.
Tissues and Body Movements
2.3
Plant Tissue
Permanent tissue
(Not dividing)
Meristematic tissue
(Actively dividing)
Apical
Lateral Intercalary
Parenchyma
Simple
Complex
Collenchyma Sclerenchyma
Phloem
Xylem
Parenchyma
Tracheids
Vessels
Fibres
Sieve tubes
Parenchyma
Fibres
Companion
cells
F i g . 2 . 3 Classification of plant tissue
2. I ntercalary Meristem: It occurs between mature tissues. In grasses, it
is responsible for the regeneration of parts eaten by grazing herbivores.
3. Lateral Meristem: It is responsible for increase in girth of plant body.
Permanent Tissue
i
Info Box!
The term ‘meristem’ is
derived from a Greek word
‘meritos’ meaning ‘divided’.
The tissues that do not undergo division are called permanent tissues.
Meristematic tissue loses its ability to divide and takes up a permanent shape, size and function.
This process is called differentiation. Thus, meristematic tissue undergoes differentiation to form
permanent tissue.
Depending on whether they are made of one type of cell or different types of cells, permanent tissues can be divided into two:
1. Simple permanent tissue
2. Complex permanent tissue
Simple Permanent Tissue
Simple permanent tissue is made up of only one type of cell. Simple permanent tissues are of
different types listed as follows.
1. Parenchyma
2. Collenchyma
3. Sclerenchyma
Chapter 2
2.4
Parenchyma
They are living tissues. The cells of parenchyma can be spherical, oval, polygonal or
elongated. Parenchymatous cells have a thin cell wall and dense cytoplasm. They are involved
in a variety of functions, like photosynthesis, gaseous exchange, food storage and other
specialized functions.
Intercellular
spaces
Cytoplasm
Nucleus
Middle lamella
Chloroplast
Vacuole
(a)
Intercellular space
(b)
F i g . 2 . 4 (a) Transverse section and (b) Longitudinal
F i g . 2 . 5 Longitudinal section of parenchyma tissue
section of parenchyma
in pumpkin (cucurbits) stem
Collenchyma
Collenchyma tissue consists of living cells. Their cell wall is irregularly thickened at the corners.
Their cells can be oval, spherical or polygonal. It gives mechanical support and flexibility to the
plants. They allow the plant to bend without breaking.
Wall
thickenings
Nucleus
Vacuole
Cell wall
Cell wall
(thickened at corners)
Chloroplast
Nucleus
Vacuole
Cytoplasm
Intercellular space
(a)
(b)
(c)
F i g . 2 . 6 (a) Transverse section, (b) Longitudinal section of collenchyma and (c) Light
microscopic cross-section of stem collenchyma
Sclerenchyma
Sclerenchyma are dead tissues. Their cells are long with narrow lumen. Their wall is thick due to
lignin deposition. Sclerenchyma provides mechanical support to the organs. It is in the fruit walls
of nuts, seed coats of legume, etc., for example, in coconut husk.
Tissues and Body Movements
Narrow lumen
Thick wall
(a)
(b)
(c)
F i g . 2 . 7 (a) Transverse section, (b) Longitudinal section of sclerenchyma and (c) Electron
micrograph of cross-section of a stem of a Buttercup, showing vascular bundle embedded in
parenchyma cells (yellow). At the outer edge of the vascular bundle is sclerenchyma tissue
Complex Permanent Tissues
Permanent tissue that is made up of more than one type of cell is called complex permanent tissue. There are two different types of complex permanent tissues: xylem and phloem.
Xylem
Xylem is involved in the transport of water and mineral nutrients that are absorbed through roots
from the soil. It also provides mechanical support to the plant. Xylem is composed of four different elements as listed below.
1.
2.
3.
4.
Xylem tracheids
Main conducting elements
Xylem vessels
Xylem parenchyma (Storage tissue and helps in lateral conduction of water)
Xylem fibres (Support)
Among the xylem elements, except xylem parenchyma, all others are dead cells.
Phloem
Phloem tissues help in the transport of photosynthesis products to various parts of the plant body.
Phloem tissue is made up of four different types of elements.
1.
2.
3.
4.
Sieve tubes
Companion cells
Parenchyma
Fibres
Among the phloem elements except phloem fibres, all are living cells. Sieve tube elements are
long, tube-like and are placed end to end. Companion cells are seen associated with sieve tube
elements. Phloem parenchyma mainly functions in storage. Phloem fibres provide mechanical
strength.
2.5
2.6
Chapter 2
One-way
only
Water and
food
Water and
minerals
Two-way flow
XYLEM
PHLOEM
F i g . 2 . 8 (a) Xylem and (b) Phloem
Epidermal Tissue
It forms the outermost covering of the plant body. It consists of compactly arranged cells.
It is usually found as single continuous layer. Epidermal surface is coated with a thick waxy layer
called cuticle, which prevents water loss. The specialized openings present on the epidermis are
called stomata. Stomata are enclosed by a pair of kidney-shaped cells called guard cells. Guard
cells regulate the opening and closing of stomata. Transpiration (loss of water in the form of water
vapour) and gaseous exchange takes place through stomata.
Stoma open
Stoma closed
Nucleus
Chloroplasts
Vacuole
Guard cell
Cell wall
Stoma
F i g . 2 . 9 Illustration of opening and closing of stomata
F i g . 2 . 1 0 Microscopic view of guard cells
and stomata in Spiderwort
Animal Tissue
Animals consist of four basic types of tissues which differ in location, structure and function as
mentioned below.
1.
2.
3.
4.
Epithelial tissue
Connective tissue
Muscular tissue
Nervous tissue
These tissues are organized in a specific manner to form different types of organs.
Tissues and Body Movements
2.7
Epithelial Tissue
Epithelial tissue provides a covering or lining for various internal and external body parts. The
cells are compactly arranged with little intercellular spaces. According to the number of cell layers, epithelial tissue is divided into two types:
1. Simple epithelium
•• Composed of single layer of cells.
•• Forms lining of body cavities, ducts and tubes.
2. Compound epithelium or stratified epithelium
•• Consists of two or more cell layers.
•• Has protective function.
According to the shape, epithelial tissue can be divided into 4 types:
1. Squamous epithelium
•• It consists of flat cells
•• It is found in walls of blood vessels, skin, etc.
2. Cuboid epithelium: It consists of cube-shaped cells and is found in lining parts of the
body, such as kidney tubules and the walls of respiratory bronchioles.
3. Columnar epithelium
•• It consists of tall pillar like cells
Info Box!
•• It is found in lining of stomach and intestine
4. Ciliated epithelium
Columnar or cuboidal cells
specialized for secretion
•• If the columnar or cuboidal cells bear cilia on their free surface, they
are called glandular epitheare called ciliated epithelium.
lium, for example, salivary
•• Cilia (hair-like projections) move back and forth to move particles out
glands.
of our body.
•• It is found in respiratory tract.
i
microvilli
F i g . 2 . 1 1 Types of epithelium
2.8
Chapter 2
Connective Tissue
Connective tissues are most abundant and function in linking, connecting or supporting other
tissues or organs in the body. The cells in connective tissues are loosely packed and are embedded
in an intercellular matrix.
Different types of connective tissues are given below.
Areolar Tissue
•• It is present beneath the skin, around blood vessels, nerves, etc.
•• It acts as a packing or supporting tissue and fills space inside organs.
F i g . 2 . 1 2 Microscopic view of areolar tissue F i g . 2 . 1 3 Microscopic view of adipose tissue
Adipose Tissue
•• It is found beneath the skin and between internal organs.
•• The excess nutrients in the body are converted into fats and are stored in this tissue.
•• The cells are called adipocytes.
Biceps
muscle
Triceps
muscle
Tendon
Bone
Ligament
F i g . 2 . 1 4 Illustration of tendon and ligament
Tendon
•• The tissues that attach muscles to bones are called
tendons.
•• They have great tensile strength and less flexibility.
Ligament
•• This tissue bones to bones.
•• It is elastic in nature.
•• It has great strength.
•• It strengthens the joint and allows normal movement.
Bone
•• They provide structural framework to the body.
•• They anchor the muscles and supports the main
organs of the body.
Tissues and Body Movements
Blood
•• It is a fluid connective tissue.
•• It consists of cells, like RBCs, WBCs and platelets.
•• Blood circulates through the blood vessels – arteries,
veins and capillaries.
•• Its function include transport of respiratory gases,
nutrients, hormones and vitamins to various parts
of body and excretory products from various parts to
kidney and liver.
F i g . 2 . 1 5 Red blood cells
F i g . 2 . 1 6 Microscopic view of bone tissue
F i g . 2 . 1 7 Microscopic view of cartilage
Cartilage
•• It smoothens bone surfaces at joints.
•• It is found in nose and ear.
Table 2.1
Differences between bone and cartilage
Bone
Cartilage
Hard
Soft
Non-elastic
Elastic
Tough
Flexible
Cells are called osteocytes
Cells are called chondrocytes
Matrix made of calcium and phosphate
Matrix made of proteins and sugar
Protects body against mechanical damage and assists in Reduces friction at joints
movement. Provides framework and shape for the body
2.9
2.10
Chapter 2
Muscular Tissue
Muscle tissue consists of many cylindrical, elongated cells called muscle fibres. Muscle fibres contract and relax in a coordinated fashion to cause movement. Muscles are of three types:
1. Skeletal muscle
•• They are attached to bones (muscles of limbs).
•• These are also known as voluntary muscles as we can contract these muscles according
to our will.
F i g . 2 . 1 8 Skeletal muscle
2. Smooth muscle
•• They are found in the wall of alimentary canal, blood vessels, etc.
•• It is not possible to contract these muscles according to our will, so these are also known as
involuntary muscles.
F i g . 2 . 1 9 Smooth muscle
3. Cardiac muscle
•• They are found only on heart walls.
•• They are involuntary in nature.
•• These muscles show rhythmic contraction and relaxation throughout life.
F i g . 2 . 2 0 Cardiac muscle
Tissues and Body Movements
2.11
Nervous Tissue
Cells of nervous tissue are called neurons. Neurons transmit information through electrical and
chemical signals. Brain, spinal cord and nerves are made up of neurons. Neurons are protected by
another type of cell called neuroglial cell. Neurons consist of three major parts:
1. Cell body: Contains nucleus and cytoplasm.
2. Axon: Longest part and carries impulses away from the cell body.
3. Dendrites: Short and branched parts arising from the cell body. They carry impulses towards cell body.
Mitochondrion
Nucleus
Cell
body
Axon
terminal
Myelin
sheath
Node of
Ranvier
Dendrite
Synapse
Schwann
cell
Axon
1. Define tissue with one example.
roups of cells either similar or dissimilar and which perform a specific function are called tissue. for
G
example, muscular tissue in humans aids in movement and locomotion.
2. Differentiate between apical meristem and lateral meristem.
Meristems are the plant tissues that can divide throughout their life.
Apical meristem
Lateral meristem
Seen at the growing tips of roots and shoots
Increases the length of root and stem
Involved in primary growth of plants
Seen along the sides of the stem and the root
Increases the girth of plant body
Involved in secondary growth of plants
Quick Recap
F i g . 2 . 2 1 A typical neuron showing all parts
2.12
Chapter 2
Body Movements
One of the important distinguishing features of living beings is movement. Movements can be
observed in both animals and plants. Movements that result in change in position is called locomotion. Animals move usually for food, shelter, mating, etc. and the methods of locomotion
depend upon their habitat and the demand of situation.
There are different kinds of structures that help in movement, such as cilia, flagella, pseudopodia
and muscles.
Cilia
Cilia are minute hair-like organelles in eukaryotic cells. Ciliary movement can be observed in
protozoans like Paramecium and also in most of our internal organs that are lined by ciliated epithelium. For example, the coordinated movement of cilia in respiratory tract helps us in removing
dust particles and foreign materials inhaled along with the atmospheric air.
F i g . 2 . 2 2 High power microscopic view of Paramecium to display hair-like cilia
Flagella
Flagella are lash-like appendages that protrude from eukaryotic and prokaryotic cells. Mammalian
sperm cell is an example for eukaryotic cell bearing flagella. Sperm cell uses its flagellum to travel
through the female reproductive tract.
F i g . 2 . 2 3 Helicobacter bacteria showing multiple flagella
Tissues and Body Movements
Pseudopodia (False Feet)
Pseudopodia are temporary projections of plasma membrane seen in eukaryotes. Cells that show
pseudopodia are usually referred to as amoeboids. Some blood cells in our body (leucocytes)
exhibit amoeboid movement. The unicellular protozoa, (amoeba) performs various activities by
the formation of pseudopodia.
Pseudopods
Nucleus
Cell membrane
F i g . 2 . 2 4 Amoeba moves with the help of pseudopodia
Muscles
Muscles are specialized tissues that contract and relax to cause movement. Muscles are of three
types skeletal, smooth and cardiac muscles. There are over 600 muscles in our body.
Skeletal muscles attach to bones at various locations and aid in movement. The contraction
and relaxation occur with the help of two proteins actin and myosin.
Biceps muscles
Triceps muscles
Ligament
Tendon
F i g . 2 . 2 5 Illustration of human muscle
2.13
2.14
Chapter 2
Skeletal System
Skeletal system comprises a framework of bones and few cartilages. Human body (adult) comprises 206 bones and the skeletal system is divided in two:
1. Axial skeleton
2. Appendicular skeleton
Skull
Mandible
Cervical vertebrae
Appendicular
skeleton
Axial
skeleton
Clavicle
Scapula
Humerus
Sternum
Rib
Ulna
Radius
Thoracic vertebrae
Lumbar vertebrae
Ilium
Sacrum
Ischium
Femur
Patella
Tibia
Fibula
F i g . 2 . 2 6 Human skeleton system
Axial Skeleton
It consists of 80 bones that are distributed along the main axis of the body. Axial skeleton includes:
•• Skull: hard protective skeleton of head.
•• Vertebral column: extends from base of the skull and protects the spinal cord.
•• Sternum: flat bone found in the centre of chest.
•• Ribs: long curved bones which form the ribcage.
Appendicular Skeleton
It supports the appendages, for example, limbs. In human body, each limb is made up of 30
bones. The bones of hands are:
••
••
••
••
••
••
Humerus
Radius
Ulna
Carpals (wrist bones)
Metacarpals (palm bones)
Phalanges (digits)
Tissues and Body Movements
The bones of lower limbs are:
•• Femur (thigh bone)
•• Patella
•• Tibia
•• Fibula
•• Tarsals
•• Metatarsals
•• Phalanges
Joints
Skull
Stemum
Ribs
Humerus
Humerus
A joint is the area where two bones are attached
for the purpose of permitting movement of body
parts. They are essential for all types of movements. There are three types of joints:
Radius
Ulna
Carpals
1. F
ibrous joints: do not allow movement, for example, joints between skull
bones.
2. Cartilaginous joints: permit limited
movement, for example, joints in vertebral column.
3. Synovial joints: allow considerable
movement. Contain a fluid-filled cavity called synovial cavity. for example,
knee joint.
Metacarpals
Phalanges
Femur
Patella
Tibia
Fibula
Tarsals
Metatarsals
F i g . 2 . 2 7 Human skeleton showing major
bones in our body
POINTS TO REMEMBER
•• Tissue is defined as a group of cells either similar or dissimilar that perform a specific
function, example epithelial tissue, muscular tissue, etc.
•• Multicellular organisms exhibit division of labour.
•• The plant tissue that can be divided throughout its life is called meristematic tissue.
•• The plant tissues that do not undergo division are called permanent tissues. Examples are
parenchyma, collenchyma, xylem, phloem, etc.
•• Animals consist of four basic types of tissues which are Epithelial, Connective, Muscular
and Nervous.
•• Movements that result in change in position is called locomotion.
•• Pseudopodia are temporary projections of plasma membrane seen in eukaryotes
•• Muscles are specialized tissues that contract and relax to cause movement.
•• Skeletal system comprises a framework of bones and few cartilages.
•• A joint is the area where two bones are attached for the purpose of permitting movement
of body parts.
2.15
2.16
Chapter 2
TEST YOUR CONCEPTS
Directions for questions 1 to 40: Fill in the blanks in
each question.
1. The second phase of mitosis is ________.
2. Meristematic tissue that increases width of plant
body is ________.
3. The dead simple permanent tissue is ________.
4. The element of xylem that provides structural support is ________.
5. The thick waxy coating present on the surface of
epidermal cells is ________.
6. Phloem parenchyma
________.
mainly
functions
in
22. Type of cell division that occurs during gamete
formation is
(a) Mitosis(b) Meiosis
(c) Binary fission
(d) Budding
23. Which of the following statements are wrong?
(i)
Mitosis involves two sequential divisions,
mitosis I and mitosis II.
7. Meristematic tissue converts to permanent tissue
through a process called ________.
(ii)Meiosis results in the formation of four daughter cells with half the number of chromosomes.
8. After meiosis ________ daughter cells are
produced.
(iii)Simple permanent tissues are made up of only
one type of cell.
9. In binary fission ________ division occurs first.
(iv)
Collenchyma provides stiffness to the plant
body.
(a) B and C
(b) A and D
(c) C and D
(d) B and D
10. Mode of cell division in prokaryotes is ________.
11. Bone tissue constitutes cells called ________.
12. Muscles seen on heart wall are ________.
PRACTICE QUESTIONS
21. Meiosis results in the formation of daughter cells
with
(a) Half the number of chromosomes.
(b) Double the number of chromosomes.
(c) One chromosome less than the parent.
(d) One chromosome higher than the parent.
13. The part of neuron which contains nucleus is
________.
14. Locomotory structure present in Paramoecium is
________.
15. Axial skeleton of the human body is made up of
________ bones.
16. The wrist bones are also known as ________
17. Long curved bones that form the ribcage are
________.
18. The joints that allow limited movement are
________.
19. The longest bone in human body is ________.
20. Skeletal muscles are under ________ control.
Directions for questions 21 to 41: For each of the following questions, four choices have been provided.
Select the correct alternatives.
24. Meristem that occurs between mature tissues is
(a) Lateral meristem
(b) Cambium
(c) Intercalary meristem
(d) Apical meristem
25. Which one the following is a dead tissue?
(a) Parenchyma
(b) Collenchyma
(c) Sieve-tube cells
(d) Xylem tracheids
26. Match the following
A Coconut husk
B Thin cell wall
C Irregularly thickened
cell wall
D Lateral conduction of
water
(a)
(b)
(c)
(d)
A
i
ii
iii
iii
B
ii
i
iv
i
C
iii
iv
ii
ii
i Xylem parenchyma
ii Collenchyma
iii Sclerenchyma
iv Parenchyma
D
iv
iii
i
iv
Tissues and Body Movements
35. The tissues that prevent friction between bones are
(a) Cartilage
(b) Blood tissue
(c) Epithelial tissue
(d) Muscle tissue
28. Which one of the following is not an element of
xylem tissue?
(a) Sieve tube
(b) Parenchyma
(c) Fibre(d) Vessels
(a) Tendon
(b) Areolar tissue
(c) Ligament
(d) Adipose tissue
29. Which of the following is a dead tissue?
37. Match the following
(a) Sieve tube
(b) Companion cells
A Adipose tissue
(c) Parenchyma
(d) Fibres
B Boneii Blood
30. The stomata are enclosed by
(a) Parenchyma
(b) Cuticle
(c) Lignin
(d) Guard cells
31. Assertion (A): Meiosis is also known as reduction
division.
Reason (R): Meiosis involves formation of
daughter cells with half the number of chromosomes than that of parent cell.
(a)Both A and R are true and R is the correct
explanation for A.
(b)Both A and R are true and R is the not the
correct explanation for A.
(c) A is true and R is false.
(d) A is false and R is true.
32. Cells present in nervous tissue that protect neurons
are
(a) Axons
(b) Neuroglial cells
(c) Osteocytes
(d) Chondrocytes
33. The matrices of bones are made up of
(a) Calcium and magnesium
36. The tissue that connects bone to bone is
C Cartilage
i Chondrocytes
iii Fat cell
D Plateletsiv Osteocyte
(a)
(b)
(c)
(d)
A
iii
iv
iii
iv
B
iv
i
i
ii
C
i
ii
iv
iii
D
ii
iii
ii
i
38. Which one of the following is a correct statement?
(a)Sperm cells use cilia to travel through female
reproductive tract.
(b)Red blood corpuscles are capable of showing
amoeboid movement.
(c)Palm bones are also known as metacarpals.
(d)
Knee joint is an example for cartilaginous
joint.
39. The hard protective covering of brain is called
(a) Vertebral column
(b) Cranium
(c) Sternum
(d) Ribs
(c)Calcium and potassium
40. Adult human body comprises
(a) 206 bones (b) 300 bones
(c) 204 bones
(d) 200 bones
(d) Calcium and phosphate
41. The kind of epithelium seen in respiratory tract is
34. Which one of the following muscles shows
rhythmic contraction and relaxation throughout
life?
(a) Skeletal muscle
(b) Cardiac muscle
(c) Heart muscle
(d) Both (b) and (c)
(a)Squamous epithelium
(b) Magnesium and phosphate
(b) Ciliated epithelium
(c)Glandular epithelium
(d) Cuboidal epithelium
PRACTICE QUESTIONS
27. The type of tissue present in coconut husk is
(a) Sclerenchyma
(b) Collenchyma
(c) Parenchyma
(d) Meristem
2.17
2.18
Chapter 2
MASTERING THE CONCEPTS
Knowledge and Understanding
1. What are stomata and what are their significance
in a plant?
2. Make a comparison between the three types of
simple permanent tissue based on their structures.
3. Differentiate between xylem and phloem.
4. Write the significance of collenchyma in plants?
5. How permanent tissue is formed from meristematic tissue?
6. What is a permanent tissue and how is it
classified?
7. What is phloem tissue, and explain its various elements with their function.
8. Give a note on cuticle.
9. Give a brief note on xylem tissue.
10. Differentiate between mitosis and meiosis.
11. Differentiate between bone and cartilage.
12. How epithelial tissues have been classified according to their shape?
13. What is ciliated epithelium, and why are they
important in the respiratory tract?
14. Make a comparison between tendon and ligament.
15. Which type of tissue is blood and what is its
function?
16. Give a note on the structure of neuron.
17. Define pseudopodia.
18. Give a note on axial skeleton.
19. What are the different types of joints and give an
example for each?
PRACTICE QUESTIONS
Application and Analysis
1. Y
ou might have seen that even after grazing by
herbivores, grasses regenerate from the remaining parts. Which tissue is responsible for this and
where it is located?
2. Further growth of an onion root stops after the
removal of tip portion. Why?
3. Identify the parts.
A
B
C
D
F
E
4. It is possible to move the elbow freely. Which
types of joints are present here that help in this
movement?
5. Plants require less energy than animals. Do you think
that this statement is correct? Explain your answer.
6. Aakanksha was shown two slides of plant tissues;
parenchyma and sclerenchyma. How did she identify sclerenchyma?
7. Generally shrubs and herbs are grown in open
places and are exposed to strong winds. But they
do not break. Why?
8. Arthritis is a common problem in aged people.
Explain its connection with movement.
9. How is an earthworm able to move without having bones?
Tissues and Body Movements
2.19
TEST YOUR CONCEPTS
1. Metaphase
22. (b)
2. Lateral meristem
23. (b)
3. Sclerenchyma
24. (c)
4. Xylem fibres
25. (d)
5. Cuticle
26. (c)
6. Storage
27. (a)
7. Differentiation
28. (a)
8. Four
29. (d)
9. Nuclear division
30. (d)
10. Binary fission
31. (a)
11. Osteocytes
32. (b)
12. Cardiac muscle
33. (d)
13. Cell body
34. (d)
14. Cilia
35. (a)
15. 80 bones
36. (c)
16. Carpal bones
18. Cartilaginous joints
38. (c)
19. Thigh bone or femur
39. (b)
20. Voluntary
40. (a)
21. (a)
41. (b)
MASTERING THE CONCEPTS
Knowledge and Understanding
1. Stomata are the specialized openings present on the
epidermis of leaves and stems. They are enclosed
by a pair of kidney-shaped cells called guard cells.
Transpiration of water and gaseous exchange takes
place through stomata.
Thin cell wall
2.
3 Xylem
Transports water and
mineral nutrients
Transport is
unidirectional, that
is, from root to upper
part of the plant body
Parenchyma
Collenchyma
Sclerenchyma
Cells can be
spherical, oval,
polygonal or
elongated
Cells can be
oval, spherical
or polygonal
Long cells with
narrow lumen
Living tissue
with nucleus
Irregularly
thickened cell
wall
Living tissue
with nucleus
Thick cell wall
Dead tissue
without nucleus
Phloem
Transports products of
photosynthesis
Multidirectional
transport from leaves
to various parts of the
plant body
PRACTICE QUESTIONS
37. (a)
17. Ribs
2.20
Chapter 2
Made up of four
elements such as:
Xylem tracheids
Xylem vessels
Xylem parenchyma
Xylem fibre
Main conducting
elements are xylem
tracheids and vessels
Three of the elements
are dead (xylem
tracheids, xylem
vessels, xylem fibres)
Made up of four
elements such as:
Sieve tube
Companion cells
Phloem parenchyma
Phloem fibres
Sieve tube elements
mainly function in
conduction
Three of the elements
are living (sieve tube,
companion cells,
phloem parenchyma)
4. Collenchyma is a type of simple permanent tissue.
It provides mechanical support and flexibility to
the plants. It also allows the plant to bend without
breaking.
5. Permanent tissue is formed by the differentiation
of meristematic tissue. The process of taking up
a permanent shape, size and specific function is
called differentiation.
PRACTICE QUESTIONS
6. The tissues that do not undergo division are called
permanent tissues. Depending on whether they
are made of one type of cell or different types of
cells, they can be classified into two types:
Simple permanent tissue: made up of only one
type of cell, for example, parenchyma, collenchyma and sclerenchyma.
Complex permanent tissues are made up of many
types of cells, for example., xylem and phloem.
7. Phloem tissue is a type of complex permanent tissue that helps in the transport of the photosynthesis products to various parts of the plant body.
Phloem tissue is made up of four different elements such as:
Sieve tubes: main conducting element.
Companion cells: seen associated with sieve tube
cells and control the functioning of sieve tube cells
Phloem parenchyma: helps in storage
Phloem fibre: provides mechanical strength
8. The thick waxy layer present in epidermal surface
is called cuticle. It prevents water loss.
9. Xylem is a type of complex permanent tissue and
is involved in the transport of water and mineral
nutrients that are absorbed through roots from
the soil. It also provides mechanical support to
the plant. Xylem is composed of four different
elements:
Main conducting
Xylem tracheids
elements
Xylem vessels
Xylem parenchyma
Xylem fibres
Storage tissue and
helps in lateral
conduction of water
Support
Among the xylem elements, except xylem parenchyma, all others are dead cells.
10. Mitosis
Involves one cycle of
division
Occurs in somatic cells
During normal cell
growth
Chromosome number
remains the same
Two daughter cells
formed
11. Bone
Hard tissue
Not elastic
Tough
Meiosis
Involves two sequential
cycles of division
Occurs in sex cells
During gamete
formation
Chromosome number
reduces to half
Four daughter cells
formed
Cartilage
Comparatively soft
Elastic
Flexible
Cells are called osteocytes Cells are called
chondrocytes
Matrix made of calcium Matrix made of
and phosphate
proteins and sugar
Protects body against
Smoothens bone
mechanical damage, assist surfaces at joints
movement
Provides framework and Reduces friction of
shape for body
joints
12. Epithelial tissues have been classified into three
types according to their shape, such as squamous,
cuboidal and columnar epithelium. Squamous epithelial tissues are made up of flat cells and are usually found in the walls of blood vessels, skin, etc.
Cuboidal cells are made up of cube-shaped cells
that are found in ducts of glands. Columnar cells
are made up of tall pillar-like cells and are usually
found in the linings of stomach and intestine.
Tissues and Body Movements
14. Tendon
Connective tissue that
attaches muscles to
bones
Less flexibility and has
great tensile strength
Ligament
Connective tissue
that attaches bones
to bones
Elastic and has great
strength
15. Blood is the fluid connective tissue and is made up
of plasma (matrix) and cells, such as RBCs, WBCs
and platelets. Blood helps in transport of various
nutrients, hormones and vitamins to different parts
of the body and also excretory products from various parts to kidney and liver.
16. Neurons are the basic unit of nervous tissue and
are made up of three major parts: cell body, axons
and dendrites. Cell body contains nucleus and
cytoplasm and possesses many short, branched
parts called dendrites. Dendrites carry impulses
towards the cell body. The longest part of neurons
that arises from cell body is called axon and it carries impulses away from the cell body.
17. Pseudopodia are temporary projections of plasma
membrane seen in eukaryotes. Cells that show
pseudopodia are usually referred to as amoeboids.
Amoeba perform various activities, such as movement, food capturing, etc., with the help of pseudopodia. Amoeboid movement is also shown by
some blood cells, such as leucocytes in human
body.
18. Human axial skeleton is made up of 80 bones that
are distributed along the main axis of the body. It
includes skull, vertebral column, sternum and ribs.
Skull functions as a hard protective covering of
the brain, whereas vertebral column extends from
base of the skull and protects the spinal cord. The
flat bone found in the centre of the chest is called
sternum and the long curved bones that form the
ribcage are called ribs.
19. Joints can be classified into three types depending
on whether they allow movement or not
Fibrous joints: do not allow movement, for
example, joints between skull bones.
Cartilaginous joints: permit limited movement,
for example, joints in the vertebral column.
Synovial joints: allow considerable movement
and contain a fluid-filled cavity called synovial
cavity, for example, knee joint.
Application and Analysis
1. The tissue responsible for the regeneration of parts
eaten by grazing herbivores is intercalary meristem. It is a kind of meristematic tissue that has
the ability to divide. Intercalary meristem is seen
between mature tissues, on either side of the nodes
and is also responsible for the increase in length of
internodes.
2. The apical meristem, meristematic tissue responsible for the increase in length of a plant body (or
here in this case root) is located at the root tip.
Removal of root tip causes the removal of apical
meristem and thus the growth of root stops.
3. A – Humerus
C – Ulna
E – Metacarpals
B – Radius
D – Carpals
F – Phalanges
4. The elbow contains synovial joint that allows considerable movement. It contains a fluid-filled cavity
with synovial fluid. This fluid helps in lubrication.
5. Plants do not have to move in search of food as
they prepare their own food through the process
of photosynthesis. Whereas, animals are dependent
on plants and other animals for food and have to
travel fulfill this requirement.
6. She could identify sclerenchyma by the thickness
of cell walls. The walls of sclerenchyma tissues are
thickened due to lignin.
7. Aerial young parts of shrubs and herbs contain
collenchyma tissues which provide flexibility and
elasticity to plants to withstand winds.
8. Arthritis condition is marked by pain in joints.
Hence, people find it difficult to move from one
place to another as joints are primarily involved in
movement of body parts.
9. During a movement, earthworm first extends front
part of the body keeping the rear portion fixed to
the ground. Then it fixes the front and releases
the rear end of the body. Earthworm has muscles
which repeatedly expand and contract to do so.
H i n t s a n d E x p l a n at i o n
13. The columnar or cuboidal epithelial cells that possess cilia on the free surface are called ciliated epithelial tissues. Cilia in the respiratory tract move
back and forth and help in removing the dust particles that are inhaled during breathing.
2.21
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Chapter
3
classification
of living
organisms
rememBer
Before beginning this chapter, you should be able to:
• Understand the need for classifying organisms
• Remember the rules for writing scientific names
• Remember the basics of two- and three-kingdom systems
of classification
key Ideas
After completing this chapter, you should be able to:
• Identify the hierarchy of classification
• Explain and apply the rules of binomial nomenclature
• Understand the five-kingdom classification
• Define the basic features of all the five kingdoms
3.2
Chapter 3
Introduction
There are a large variety of living organisms in the world. It is nearly impossible to study all of
them individually, but grouping them into convenient categories makes their studies possible. This
process is known as classification. Grouping or classification is done on the basis of some observable
characters. The scientific term used to represent these categories is called taxa. Classification of
living organisms into different taxa on the basis of their characteristics is called taxonomy.
Hierarchy of classification
Hierarchy is the taxonomical classification of living organisms into successive levels of complexity.
There are seven levels of categories where ‘kingdom’ is the highest level and species is the lowest
level. The various categories are as follows:
Species: A group of individual organisms with fundamental similarities is called species, for
example, all mango plants are included in one species.
Genus: It consists of a group of related species that have some common characters, for example,
tiger and lion come under the same genus ‘Panthera’.
Family: It consists of a group of related genera, for example, lion, tiger and cat are included in
the same family, that is, Felidae.
Order: A group of related families constitutes an order, for example, family Canidae (dogs) and
Felidae (cats) come under the same order Carnivora.
Class: It consists of related orders, for example, class Mammalia includes orders Carnivora and
Primata (apes, monkeys and humans).
Phylum: In animals, related classes are categorized into the phylum, whereas in plants they are
categorized into divisions, for example, phylum Chordata constitutes of mammals along with
birds, reptiles, amphibians and fish.
Kingdom: Phyla that have common characters are grouped into various kingdoms, such as plant
kingdom (Plantae) or animal kingdom (Animalia).
Kingdom
Phylum
Class
Order
Family
Genus
Species
Fi g . 3 . 1 Taxonomic hierarchy in increasing order
Classification of Living Organisms
The levels of taxonomic hierarchy are explained with examples in the following figure:
Species
Genus
Family
Lion
Tiger
Cat
leo
tigris
Panthera
Wolf
Human
catus
lupus
sapiens
Felis
Canis
Homo
canidae
hominidae
felidae
Order
primata
carnivora
mammalia
Class
Phylum
chordata
Kingdom
animalia
Fi g . 3 . 2 Taxonomic hierarchy of different animals
Binomial nomenclature
The formal system of naming a living organism by giving it a name composed of two parts is
called binomial nomenclature. This naming system was put forward by Carolus Linnaeus in his
book Systema Naturae in the year 1758. He is regarded as the ‘father of taxonomy’. Binomial
names or scientific names are mostly derived from latin but they can be based from other languages too. The first part of a scientific name represents the genus to which the species belong
and the second part represents the species within the genus. When handwritten, the first letter
of the first part, the genus, is always capitalized while the species name is not. However, both the
genus and species name are always italicized.
For example, the scientific name of human is Homo sapiens, where Homo represents the genus
and sapiens represents the name of species. Similarly, the scientific name of mango is Mangifera
indica, where Mangifera represents genus and indica represents species.
The taxonomic hierarchy of human beings is explained as an example for better understanding.
3.3
3.4
Chapter 3
Table 3.1 Taxonomic hierarchy of human beings
Taxonomic Rank
Example
Kindom
Phylum
Class
Order
Family
Genus
Species
Common name
Animalia
Chordata
Mammalia
Primate
Hominidae
Homo
sapiens
Human
Universal Rules of Nomenclature
The rules followed while giving scientific names to organisms are explained below:
•• Biological names are generally Latin and are printed in italics and if handwritten, the genus
and species names are separately underlined.
•• The genus name starts with a capital letter, whereas the species name is written in lower
case.
•• Name of the author appears after the species name and is written in an abbreviated
form, for example, Mangifera indica Linn. indicates that the species was first described by
Linnaeus.
Scientific Name
Two parts
Genus Name
Species Name
Starts with
capital letter
Starts with
lower case
Homo
sapiens
Fi g . 3 . 3 Division of a scientific name
Need for Binomial Nomenclature
The living organisms, plants or animals, are usually known by their local names in a particular
locality. The local names may vary from place to place, which can lead to confusion in identifying
the organisms. So in order to avoid this confusion, standardized naming is required. Providing a
standard name that is universally accepted will help us in identifying the organism with the same
name all over the world.
Classification of Living Organisms
History of Classification
Aristotle, the Greek scientist, was one of the earliest scientists to classify living organisms on the
basis of some simple morphological characters. He is known as the ‘father of biology/zoology’.
He classified the living organisms into two groups, plants and animals. He further divided plants
into trees, shrubs and herbs. Similarly, animals are divided into two groups: one with red blood
and the other one without red blood. He also classified animals on the basis of their habitats, such
as aquatic, terrestrial and aerial.
Aristotle’s Classification
Living Organisms
Aquatic
Plants
Habitat
Animals
Terrestrial
Aerial
Trees
Shrubs
Herbs
With red
blood
Lack red
blood
Fi g . 3 . 4 Aristotle’s classification of living organisms
Theophrastus, Aristotle’s student, is known as the ‘father of botany’ for his works on plants.
Contributions of Theophrastus are also profound in the history of plant classification. Aristotle’s
classification had many demerits as many organisms do not fit to the groups. For example, frogs,
when born, live in water and adult frogs live on land. Even with the limitations, Aristotle’s system
of classification was used until it was replaced by the classification system proposed by Carolus
Linnaeus.
Two-kingdom Classification
Two-kingdom classification, which was used until recently, was introduced by Linnaeus. He
classified all organisms into two kingdoms on the basis of nutrition and locomotion. The two
kingdoms were Animalia (for animals) and Plantae (for plants).
Linnaeus Two-kingdom Classification
In the 18th century, Carolus Linnaeus published a system for classification of organisms. He classified the organisms into 2 kingdoms—Animal kingdom and Plant kingdom, on the basis of their
nutrition and locomotion.
Living organisms
(Based on Nutrition and Locomotion)
Animalia
Plantae
Fi g . 3 . 5 Division of organisms in two-kingdom classification
3.5
3.6
Chapter 3
However their were certain demerits of the two-kingdom classification which are listed below:
•• This system did not distinguish between
~~ prokaryotes and eukaryotes
~~ unicellular and multicellular organisms
~~ photosynthetic and non-photosynthetic organisms
•• A large number of organisms did not fall into any category, for example, Euglena (unicellular)
had characters of both plants and animals.
Three-kingdom Classification
Since the two-kingdom classification proposed by Linnaeus was not so successful, a new
three-kingdom classification was developed by a German biologist Ernst Haeckel in 1886. The
three kingdoms according to Haeckel were:
1. Kingdom Plantae
2. Kingdom Animalia
3. Kingdom Protista
While the first two kingdoms were same as in the older classification, a new kingdom of unicellular microorganisms was introduced. Kingdom Protista included protozoa, fungi, bacteria and
other microorganisms. Protists are primarily aquatic in nature.
Five-kingdom Classification
Five-kingdom classification was proposed by an American ecologist, R.H. Whittaker (1969).
The main criteria for this classification were as follows:
••
••
••
••
••
Cell type
Cell wall
Nuclear membrane
Body organization
Mode of nutrition
Organism
Prokaryote
Unicellular
Eukaryote
Unicellular
Multicellular
Monera
Protista
With cell wall
Without cell wall
Animalia
No photosynthesis
Fungi
Perform photosynthesis
Plantae
Fi g . 3 . 6 Flow chart showing five-kingdom classification
Classification of Living Organisms
The five kingdoms are as follows:
1.
2.
3.
4.
5.
Monera
Protista
Fungi
Plantae
Animalia
Animalia
Plantae
Monera
Organisms
Fungi
Protista
Fi g . 3 . 7 The five-kingdom classification of organisms
Monera
It includes prokaryotic organisms (bacteria), that is, both archaebacteria and eubacteria.
Archaebacteria are found in most harsh habitats, such as extremely salty area. Eubacteria are the
true bacteria, which are found everywhere including the human body.
It has the following features:
••
••
••
••
••
Prokaryotic
Mostly unicellular
Cell wall present
Nuclear membrane absent
Mode of nutrition can be autotrophic (produce their own food) or heterotrophic (depend
on others for food)
Pilus
Ribosome
Capsule
Flagellum
Cell wall
Nucleoid (DNA)
Cell membrane
Fi g . 3 . 8 Bacterium—A Moneran
3.7
3.8
Chapter 3
Protista
All single-celled eukaryotes are included in this kingdom. Members of this kingdom are mostly
aquatic. It has the following features:
••
••
••
••
••
Eukaryotic and unicellular
Presence of cell wall in some members
Presence of nuclear membrane
Cellular level of body organization
Both autotrophic and heterotrophic organisms come under this kingdom, for example,
Amoeba and Paramoecium.
Paramoecium—A Protist
Amoeba—A protist
Fi g . 3 . 9 Some common protists
Fungi
Most of the fungi are multicellular organisms but unicellular fungi are also found such as yeast.
It has the following features:
••
••
••
••
Eukaryotic in nature
Presence of cell wall which is made up of chitin
Nuclear membrane present
Heterotrophic in nature, either saprophytic (feeds on dead and decaying matter) or parasitic
(derives food from host organisms), for example, yeast and mushrooms.
Yeast—A unicellular fungi
Mushroom—A multicellular fungi
Fi g . 3 . 1 0 Some common fungi
Classification of Living Organisms
Plantae
All eukaryotic, chlorophyll-containing organisms are included in this kingdom, that is, all plants.
They are multicellular and contain cells with cell wall.
Kingdom Plantae includes the following:
1.
2.
3.
4.
5.
Algae
Bryophytes
Pteridophytes
Gymnosperms
Angiosperms
Algae
Angiosperms
Bryophytes
Kingdom
Plantae
Gymnosperms
Pteridophytes
Fi g . 3 . 1 1 Divisions of plant kingdom
Algae: They are simple, chlorophyll-bearing organisms that range from unicellular to multicellular. Plant body is in the form of a thallus, i.e no clear distinction of true roots, stems and leaves.
Most of the algae are autotrophs (synthesize their own food by the process of photosynthesis).
They are mostly aquatic, for example, Spirogyra. Some of them are also found on rocks or within
plants and animals, for example, lichens.
Bryophytes: It is the collective term used for hornworts, liverworts and mosses. They are
the simplest and most primitive land plants. As, they are terrestrial but need water for completing their life cycle, they are called amphibians of plant kingdom. In these, plants possess
stem-like and leaf-like structures but lack xylem and phloem (vascular tissues), for example,
moss. They prefer to grow in shady and damp places.
Pteridophytes: These were the first plant group to have true vascular system for the conduction
of water, minerals and food. The word pteridophyte comes from the word ‘Pteron’ meaning
feather and ‘phyton’ meaning plant. Thus, pteridophytes are those plants which possess feather
like leaves, for example, ferns.
Gymnosperms: These are vascular plants which produce naked seeds (not encased), that is seeds
are not enclosed in fruits. Gymnosperms produce male and female cones, which produce pollen
grains and eggs, respectively. Male cones are generally smaller than female cones, for example,
pines.
Angiosperms: These are flowering plants which reproduce through seeds which develop inside
fruits. The reproductive structure i.e. the flower houses both the male and female reproductive
organs. The flower which has both male and female organs are called perfect flower, for example,
apples, cherries, orchids, etc. The flower which has only either male or female organ is called
imperfect flower, for example, cucumber and corn.
3.9
3.10
Chapter 3
Euglena
(Algae)
Moss
(Bryophytes)
Pine
(Gymnosperm)
Fern
(Pteridophytes)
Orchid flower
(Angiosperm)
Fi g . 3 . 1 2 Examples of different divisions under plant kingdom
Animalia
All eukaryotic, multicellular and heterotrophic animals come under this category. They lack
cell wall. Most of them show mobility. Kingdom ‘Animalia’ is divided into different phyla as
described below:
Porifera
Coelenterata
Chordata
Hemichordata
Echinodermata
Ctenophora
Platyhelminthes
Animalia
Mollusca
Aschelminthes
Arthropoda
Annelida
Fi g . 3 . 1 3 Different phyla under animal kingdom
Classification of Living Organisms
Porifera: They are pore-bearing organisms (i.e., they have holes on their body). They are commonly known as sponges. The food, oxygen, etc., reach the body by a water current through the
holes.
Coelenterata (Cnidaria): They are aquatic animals that can be either nonmotile or free swimming. They got the name due to the presence of specialized cells called cnidoblasts or cnidocytes
on their body, for example, Hydra and jellyfish.
Ctenophora: They are commonly known as comb jellies and are exclusively marine. They have
the ability to emit light (bioluminescence), for example, Ctenoplana and Pleurobrachia.
Sycon (Porifera)
Jellyfish (Cnidaria)
Comb jelly (Ctenophora)
Fi g . 3 . 1 4 Examples of phylum porifera, cnidaria and ctenophora
Platyhelminthes: They are commonly known as flatworms as they have a flattened body. They
are mostly found as endoparasites in animal’s body, for example, tapeworm.
Aschelminthes: They are also called roundworms as their cross-sections are round in shape.
They can be aquatic or terrestrial, free living or parasitic, for example, Ascaris.
Annelida: They may be aquatic or terrestrial. Their body is divided into many segments, and this
type of segmentation is called metamerism, for example, earthworm.
Liver fluke (Platyhelminthes)
Ascaris (Aschelminthes)
Earthworm (Annelida)
Fi g . 3 . 1 5 Examples of phylum platyhelminthes, aschelminthes and annelida
Arthropoda: They are the largest group of animals. They show segmentation in their body. The
significant feature of phylum ‘Arthropoda’ is the presence of ‘jointed legs’, for example, prawns
and butterflies.
Mollusca: They are the second largest phylum of animal kingdom. They can be terrestrial,
marine or freshwater, for example, octopus and snails.
3.11
3.12
Chapter 3
Honey bee
Spider
Millipede
Prawn
Crab
Fi g . 3 . 1 6 Some examples of phylum arthropoda
Echinodermata: They are spiny-skinned organisms and are exclusively marine animals, for
example, starfish.
Hemichordata: This group includes worm-like marine animals, for example, Balanoglossus.
Snail (Mollusca)
Starfish (Echinodermata)
Fi g . 3 . 1 7 Examples of phylum mollusca, echinodermata and hemichordata
Chordata: The organisms under this phylum are characterized by the presence of notochord
(flexible rod-like structure), which later develops into a vertebral column. Notchord appears in
the embryonic stage and in adults is converted to backbone.
Classification of Living Organisms
Phylum chordata includes the following classes:
1. Pisces (fish)
3. Reptilia (crocodiles)
5. Mammalia (humans)
2. Amphibia (frogs)
4. Aves (birds)
Fish (Pisces)
Frog (Amphibian)
Fi g . 3 . 1 8 Examples of classes pisces and amphibia
Crocodile (Reptilia)
Flock of birds (Aves)
Humans (Mammalia)
Fi g . 3 . 1 9 Examples of classes reptilia, aves and mammalia
Table 3.2
Characteristics of five kingdoms
Characters Monera
Protista
Fungi
Cell type
Cell wall
Prokaryote
Present
Nuclear
membrane
Body
organization
Mode of
nutrition
Absent
Eukaryote
Present in
some
Present
Eukaryote
Eukaryote
Present (chitin) Present
(cellulose)
Present
Present
Unicellular
Unicellular
Autotrophic
and
heterotrophic
Bacteria
Unicellular/
multicellular
Heterotrophic
Autotrophic
and
heterotrophic
Amoeba
Yeast
Examples
Plantae
Animalia
Eukaryote
Absent
Present
Multicellular
Multicellular
Autotrophic
Heterotrophic
All green
plants
Birds,
humans, etc.
3.13
Quick Recap
3.14
Chapter 3
1. Define the terms taxonomy and taxa.
he wide variety of living organisms present on the earth can be grouped into different categories on the baT
sis of some observable characters. The scientific terms used to represent these categories are called taxa. The
classification of living organisms into different taxa on the basis of their characteristics is called taxonomy.
2. What does it mean by hierarchy of classification?
he taxonomical classification of living organisms into successive levels of complexity is called hierarchy
T
of classification. There are seven levels of categories, such as species, genus, family, order, class, phylum
and kingdom. Species is the lowest level, whereas kingdom is the highest level.
3. What is genus and give an example?
group of related species sharing some common characters constitutes the genus, for example, genus
A
Panthera includes species of tigers and lions.
4. What is binomial nomenclature?
aming a living organism by giving it a scientific name made up of two parts is called binomial nomenN
clature. Each name consists of two parts, that is, genus and species names. This system was introduced
by Carolus Linnaeus, for example, the scientific name of human is Homo sapiens, where Homo represents
genus and sapiens represents species.
5. A brief note on five-kingdom classification.
ive-kingdom classification is the classification of living organisms into five kingdoms, such as Monera,
F
Protista, Fungi, Plantae and Animalia. This method of classification was proposed by R. H. Whittaker.
The main criteria for classification are as follows:
••
••
••
••
••
Cell type
Cell wall
Nuclear membrane
Body organization
Mode of nutrition
6. What are different phyla under kingdom ‘Animalia’ and give examples for each?
Porifera Sponges
Coelenterata
Hydra
Ctenophora
Ctenoplana
Platyhelminthes Tapeworms
Aschelminthes
Ascaris
Annelida
Earthworms
Arthropoda
Insects
Mollusca
Octopus
Echinodermata Starfish
Hemichordata
Balanoglossus
Chordata
Humans
7. Write a note on the phylum ‘Arthropoda’.
They are the largest group of animals. They show segmentation in their body. The significant feature of
phylum ‘Arthropoda’ is the presence of ‘jointed legs’, for example, prawns and butterflies.
3.15
8. What is the unique character of phylum ‘Chordata’?
The organisms under this phylum are characterized by the presence of notochord (flexible rod-like structure), which later develops into a vertebral column. Notochord appears in the embryonic stage and in
adults it is converted to backbone.
9. What are roundworms and why are they called so?
The organisms that come under phylum ‘Aschelminthes’ are also called roundworms as their cross-sections are round in shape. They can be aquatic or terrestrial, for example, Ascaris.
10. Define metamerism and give an example of organisms that show metamerism.
Metamerism is the segmentation of body into a number of segments, for example, earthworms.
POINTS TO REMEMBER
•• Classification of living organisms into different taxa on the basis of their characteristics is
called taxonomy.
•• Hierarchy is the taxonomical classification of living organisms into successive levels of
complexity. There are seven levels of categories where ‘kingdom’ is the highest level and
‘species’ is the lowest level.
•• The formal system of naming a living organism by giving it a name composed of two parts
is called binomial nomenclature.
•• Five-kingdom classification is the classification of living organisms into five kingdoms, such
as Monera, Protista, Fungi, Plantae and Animalia.
•• Kingdom Monera includes single-celled prokaryotic organisms (bacteria), that is, both
archaebacteria and eubacteria.
•• Kingdom Protista includes all single-celled eukaryotes, like Amoeba and Paramoecium.
•• Kingdom Fungi includes saprotrophytic and multicellular organisms like mushrooms but
unicellular fungi are also found such as yeast.
•• All eukaryotic, chlorophyll-containing organisms are included in plant kingdom, that is all plants.
•• All eukaryotic, multicellular and heterotrophic animals come under animal kingdom,
example tiger, octopus, insects, etc.
Quick Recap
Classification of Living Organisms
3.16
Chapter 3
TEST YOUR CONCEPTS
Directions for questions 1 to 20: Fill in the blanks in
each question
1. A group of related genera is called ________.
2. Cat and tiger belong to the family ________.
3. Monkeys and humans come under the order
________.
4. Binomial nomenclature
________.
was
introduced
by
5. The part of scientific name that starts with capital
letter is ________.
6. ________ is known as the father of botany.
7. Organisms that can synthesize their own food are
called ________.
8. The cell wall of fungi is made up of ________.
9. Chlorophyll-bearing eukaryotes come under the
kingdom ________.
10. ________ are known as amphibians of plant
kingdom.
11. Platyhelminthes are also called ________.
12. ________ is the largest phylum of animals.
PRACTICE QUESTIONS
13. Spiny skinned organisms come under the phylum
________.
14. The flexible rod-like structure present in organisms under phylum ‘Chordata’ is ________.
15. According to the mode of nutrition, organisms
under kingdom ‘Animalia’ are ________.
22. Select the mismatch
A
B
C
D
Lion
Catus
Wolf
Tiger
-
Panthera
Felis
Felis
Canis
(a) A and B
(b) C and D
(c) A and C
(d) B and C
23. Identify the wrong statement.
(a)
If handwritten, the genus and the species
names are underlined together.
(b)Genus name always starts with a capital letter.
(c) Species name starts with lower case.
(d)
Binomial nomenclature was proposed by
Carolus Linnaeus.
24. The father of zoology is
(a) Carolus Linnaeus
(b) Theophrastus
(c) Aristotle
(d) Whittaker
25. Which one of the following comes under the
kingdom ‘Monera’?
(a) Yeast(b) Algae
(c) Mosses(d) Rhizobium
26. The organisms that feed on dead and decaying
matter are known as
(a) Autotrophs
16. Pore-bearing organisms come under the phylum
‘________’.
(b) Parasites
17. The ability to emit light is called ________.
(d) None of the above
18. Octopus comes under the phylum ________.
19. Jelly fish comes under the phylum ________.
20. The presence of jointed legs is the characteristic
feature of phylum ‘________’.
Directions for questions 21 to 40: For each of the following questions, four choices have been provided.
Select the correct alternative.
(c) Saprophytes
27. Find out the word pair relationship.
________: Monera
Mushroom: ________
28. Amoeba and Paramoecium come under the kingdom
(a) Plantae(b) Protista
(c) Monera(d) Fungi
21. Which one of the following is not a name of
family?
29. Plants that lack xylem and phloem are called
(a) Felidae(b) Canidae
(a) Bryophytes
(b) Angiosperms
(c) Mammalia (d) Hominidae
(c) Gymnosperms
(d) Pteridophytes
Classification of Living Organisms
A Aristotle
i Two-kingdom classification
(c) iii
(d) ii
B Theophrastus
ii Father of zoology
34. Bioluminescence was shown by the phylum
C Linnaeus
iii Five-kingdom classification
(a) Porifera(b) Ctenophora
D Whittaker
iv Father of botany
(c) Coelentrata
(a)
(b)
(c)
(d)
C
i
i
iii
ii
35. Identify the word pair relationship.
________: Annelida
Jointed legs: ________
A
iv
ii
ii
iii
B
iii
iv
i
i
D
ii
iii
iv
iv
31. Which one of the following is exclusively marine?
(a) Mollusca
(b) Echinodermata
(c) Aschelminthes
(d) Coelenterata
32. Organisms under phylum ‘Ctenophora’ are also
known as
(a) Roundworms
(b) Comb jellies
(c) Ctenoplana
(d) Flatworms
33. Match the following:
A.
B
C
D
Octopus
Starfish
Balanoglossus
Chelone
i
ii
iii
iv
Reptilia
Hemichordata
Mollusca
Echinodermata
B
iv
iii
C
ii
i
iv
i
i
iii
(d) Mollusca
36. The second largest phylum is
(a) Arthropoda
(b) Chordata
(c) Echinodermata
(d) Mollusca
37. Which one of the following is not a member of
phylum ‘Chordata’?
(a) Crocodile
(b) Columba
(c) Macropus
(d) Pleurobrachia
38. Phylum ‘Porifera’ is commonly called
(a) Colelenterata
(b) Sponges
(c) Comb jellies
(d) Vertebrata
39. Class ‘Mammalia’ includes
(a) Fish
(b) Frogs
(c) Birds
(d) Humans
40. Worm-like marine animals come under the
phylum
Option
A
(a) iii
(b) iv
ii
iv
D
i
ii
(a) Hemichordata
(b) Pisces
(c) Echinodermata
(d) Flat worms
MASTERING THE CONCEPTS
Knowledge and Understanding
1. Write a note on the various features of kingdom
‘Monera’.
5. Write a note on the various features of kingdom
‘Protista’.
2. What are the differences between organisms under
kingdom ‘Plantae’ and kingdom ‘Fungi’?
6. What are bryophytes and pteridophytes?
3. Write a note
classification.
8. What is notochord and write its significance.
4. What are main
classification?
on
Linnaeus’ two-kingdom
7. Write a note on the phylum ‘Cnidaria’.
9. List out the main features of kingdom ‘Animalia’.
criteria
for
five-kingdom
10. What are the different classes under phylum
‘Chordata’? Give examples for each.
PRACTICE QUESTIONS
30. Match the following
3.17
3.18
Chapter 3
Application and Analysis
1. Whittaker’s five-kingdom classification was a
more logical method of classification as compared to two-kingdom classification. Justify the
statement.
2. Some of the organism’s names are jumbled in the
box given below. Arrange these terms correctly in
the column that follows.
PRACTICE QUESTIONS
Ascaris
Snails
Roundworms Ctenoplana
Jellyfish
Pleurobrachia Starfish
Octopus
Balanoglossus Rana
Macropus
Chelone
Phylum
Example
Cnidaria
Ctenophora
Aschelminthes
Mollusca
Echinodermata
____________________
____________________
____________________
____________________
____________________
Hemichordata
Chordata
____________________
____________________
3. Ravi decides to make notes on a group of 20 different living organisms which he observes on a
daily basis. How can the knowledge of taxonomy
be helpful in this exercise?
4. Dogs and cats are different from each other. At
the levels of hierarchy, are they grouped under any
common taxon?
5. Tiger and lion have scientific names, Panthera tigris
and Panthera leo, respectively. What similarities
could be identified?
6. Bryopsida is called amphibian of the plants. What
can be inferred about this plant?
7. Plant body in higher plants is well-developed.
Roots are the organs used for absorbing water and
minerals. What is the equivalent of roots in the less
developed lower plants?
Classification of Living Organisms
3.19
1. Family
21. (c)
2. Felidae
22. (b)
3. Primata
23. (a)
4. Carolus Linnaeus
24. (c)
5. Generic name
25. (d)
6. Theophrastus
26. (c)
7. Autotrophs
27. Bacteria, Fungi
8. Chitin
28. (b)
9. Plantae
29. (a)
10. Bryophytes
30. (b)
11. Flatworms
31. (b)
12. Arthropoda
32. (b)
13. Echinodermata
33. (a)
14. Notochord
34. (b)
15. Heterotrophs
35. Metamerism, Arthropoda
16. Porifera
36. (d)
17. Bioluminescence
37. (d)
18. Mollusca
38. (b)
19. Cnidaria
39. (d)
20. Arthropoda
40. (a)
MASTERING THE CONCEPTS
Knowledge and Understanding
1. Kingdom ‘Monera’ includes both archaebacteria
and eubacteria. The main features are as follows:
•• Unicellular Body Organization
•• All are prokaryotic in nature (without a welldefined nucleus).
•• Presence of cell wall around the cell.
•• Absence of nuclear membrane.
•• Some of the organisms that come under
kingdom ‘Monera’ can produce their own food
(autotrophs) and some
other
organisms
depend on others for food (heterotrophs).
2. Plantae
Fungi
Include multicellular Include both unicellular
organisms
and multicellular
organisms
Cell wall made up of Cell wall made up of
cellulose
chitin
Autotrophs
Heterotrophs
For example, Fern, For example, yeast,
mosses
mushroom
H i n t s a n d E x p l a n at i o n
TEST YOUR CONCEPTS
3.20
Chapter 3
3. Linnaeus classified living organisms into two kingdoms based on nutrition and locomotion. The two
kingdoms were as follows: Animalia and Plantae.
The organisms that are autotrophs (produce their
own food) and are not capable of locomotion were
placed under kingdom ‘Plantae’ and the organisms
that are heterotrophs (or depend on others for
food) and can move were placed under the kingdom ‘Animalia’. The two-kingdom classification
had some demerits as the system failed to distinguish between
•• Prokaryotes and eukaryotes.
•• Unicellular and multicellular organisms.
Besides this, a large number of organisms do not
fall into any category, for example, Euglena, as they
have characters of both animals and plants.
H i n t s a n d E x p l a n at i o n
4. Five-kingdom classification was proposed by R.
H. Whittaker and the main criteria for classification were as follows:
••
••
••
••
Cell type (prokaryote or eukaryote).
Body organization: unicellular or multicellular.
Cell wall (whether cell wall is present or not).
Nuclear membrane (whether a well-defined
nucleus surrounded by nuclear membrane is
present or not).
•• Mode of nutrition (autotrophs or heterotrophs).
5. All single-celled eukaryotes are included in the
kingdom ‘Protista’. Members are mostly aquatic.
Features are as follows:
••
••
••
••
Presence of cell wall in some members.
Presence of nuclear membrane.
Cellular level of body organization.
Both autotrophic and heterotrophic organisms
come under kingdom ‘Protista’, for example,
Amoeba and Paramoecium.
6. Bryophytes and pteridophytes come under kingdom ‘Plantae’. Bryophytes are usually known as
‘amphibians of plant kingdom’. They possess
stem and leaf-like structure but lack vascular tissues (xylem and phloem), for example, moss.
Pteridophytes possess root, stem, leaves and also
specialized tissues for conduction of water and
other substances, for example, fern.
7. They are aquatic animals that can be either nonmotile or free swimming. They got the name due
to the presence of specialized cells called cnidoblasts or cnidocytes on their body, for example,
Hydra and jellyfish.
8. Notochord is the flexible rod-like structure that
later develops into a vertebral column. The organisms that possess notochord come under the phylum ‘Chordata’. Notochord appears in the embryonic stage and is later converted into backbone
(vertebral column).
9. The main features of organisms under kingdom
‘Animalia’ are given as follows:
•• All are eukaryotic with a well-defined nucleus.
•• Multicellular.
•• Heterotrophic nutrition (depend on others for
food).
•• Lack cell wall.
•• Most of them show mobility.
•• For example, birds and human.
10. The different classes under phylum ‘Chordata’ are
as follows:
Pisces
Amphibia
Reptilia
Aves
Mammalia
–
–
–
–
–
Fish
Frogs
Crocodiles
Birds
Humans
Application and Analysis
1. Two-kingdom classification was proposed by
Carolus Linnaeus. He classified all organisms into
two kingdoms on the basis of nutrition and locomotion. The two kingdoms were ‘Animalia’ (for
animals) and ‘Plantae’ (for plants).
His system of classification had some demerits
such as:
•• This system did not distinguish between:
- eukaryotes and prokaryotes,
- unicellular and multicellular organisms,
- photosynthetic and non-photosynthetic organisms.
•• A large number of organisms did not fall into
any category, for example, Euglena (unicellular)
had characters of both plants and animals.
Classification of Living Organisms
••
••
••
••
••
Cell type
Cell wall
Nuclear membrane
Body organization
Mode of nutrition
Organisms that are prokaryotes and unicellular in
nature were placed under kingdom ‘Monera’.
Eukaryotic unicellular organisms were placed
under kingdom ‘Protista’. Eukaryotic heterotrophic organisms that included both unicellular
and multicellular organisms were placed under
kingdom ‘Fungi’. Multicellular organisms that
can perform photosynthesis were placed under
kingdom ‘Plantae’. Eukaryotic organisms that
are multicellular and heterotrophic in nature
were placed under kingdom ‘Animalia’. They
lack cell wall. Thus, more accurate method for
classification was possible through five-kingdom
classification.
2. Phylum
Example
Cnidaria
Jellyfish
Ctenophora
Ctenoplana, Pleurobrachia
Aschelminthes
Ascaris, Roundworms
Mollusca
Octopus, Snails
Echinodermata
Starfish
Hemichordata
Balanglossus
Chordata
Rana, Macropus, Chelone
3. Ravi can broadly classify the organisms on the basis
of the kingdom they belong to. After categorizing
them into plants and animals, he can further group
them according to their specific physical characters
and features. For example, he can group trees and
shrubs under kingdom Plantae and all the animals
under kingdom Animalia. And so on, he can make
further sub-groups with the help of knowledge of
hierarchy of classification.
4. Cats and dogs are grouped under the same order
Carnivora. Both the animals are meat-eating
organisms. On the basis of this similarity, they are
grouped under the same order.
5. Both lion and tiger belong to the same Genus, that
is, Panthera. They are characterized by similar cranial (related to brain) features.
6. Since Bryopsida is called amphibian of the plant
kingdom, it must be a bryophyte. Bryophytes live
in soil (land) but they require water as a medium
to reproduce. Hence, they are called amphibians of
plant kingdom.
7. Lower plants have thallus-like structures, for example, algae. Thallus has root-like structures called
rhizoids that serve the purpose of roots.
H i n t s a n d E x p l a n at i o n
These demerits were rectified in five-kingdom
classification, which was proposed by R. H
Whittaker. The main criteria for classification
were as follows:
3.21
This page is intentionally left blank.
Chapter
4
reproduction
in Animals and
plants
remember
Before beginning this chapter, you should be able to:
• Recall the basic concept of evolution
• Remember different modes of reproduction
keY IdeAs
After completing this chapter, you should be able to:
• Describe the process of reproduction in animals
• Understand the concepts of adolescence and puberty
• Describe the process of reproduction in plants
4.2
Chapter 4
Introduction
The world we live in consists of living as well as non-living components and the striking difference between these two is the ability of living organisms to produce individuals of their own
kind. This ability of living organisms is essential for their survival. Reproduction is a biological
process by which an organism gives birth to its younger ones. It is important for the continuation
of generations of living organisms on earth. It is a vital process without which species cannot
survive for long. Reproduction is mainly of two types:
1. Asexual reproduction:
(i) Simple mode of reproduction.
(ii) Usually only one parent is involved.
(iii) Younger ones produced are exactly identical to parents and are called clones.
2. Sexual reproduction:
(i) Not as simple as asexual reproduction.
(ii) Usually two parents are involved.
(iii) Younger ones produced are not identical to parents but resemble both parents.
Reproduction in Animals
There are two modes of reproduction in animals. They can reproduce either by asexual reproduction in which only one individual is involved or sexual reproduction in which two individuals are
involved. These are explained in detail in the following section.
Asexual Reproduction
Asexual reproduction can be observed in small animals, like hydra, amoeba, etc. There are different modes of asexual reproduction. Some of them are given below:
Binary Fission
•• This involves division of a parent organism into two younger ones, for example, Amoeba
and Paramoecium.
~~ Reproduction in amoeba involves division of nucleus into two nuclei, followed by
division of cytoplasm into two; so that each part receives a nucleus.
~~ Other organism that can reproduce by binary fission is Paramoecium.
Parent cell
Nucleus divides
Cytoplasm divides
Two daughter cells
F i g . 4 . 1 Binary fission in Amoeba
Budding
•• Involves development of a new organism from the buds formed in parent’s body, for
example, Hydra, yeast, etc.
~~ In hydra, a bud develops as an outgrowth that later on develops into new hydra. New
offspring remains attached to parent body and detaches only after it is fully matured.
Reproduction in Animals and Plants
Bud
Developing
bud
Fully matured
hydra
Detached
young hydra
F i g . 4 . 2 Budding in hydra
Fragmentation
•• Here, the parent body breaks into different fragments and each fragment develops into an
organism, for example, star fish.
F i g . 4 . 3 Fragmentation in starfish
Sexual Reproduction
Sexual reproduction is a kind of reproduction where two parents are involved with fusion of
male and female gametes. Gamete is a cell that can fuse with another gamete of opposite sex to
form zygote that develops into a younger one. Usually the male and female gametes are produced
by two different individuals. But in some cases, both are produced by a single organism. Such
organisms are called hermaphrodites (bisexual). A hermaphrodite possesses both male and female
reproductive organs, for example, earthworm. Organisms that possess either male or female
reproductive organs alone are called unisexual organisms, for example, humans.
Male Reproductive Organs
In humans, the male reproductive organs include testes, scrotum, sperm ducts, accessory sex
glands and penis.
Testes: A pair of testes are the male gonads that produce the male gametes called sperms. Millions
of sperms are produced by the testes. They also produce testosterone, which is the primary male
sex hormone.
Scrotum: It is a sac-like organ that houses the testes. It is present outside the body and maintains
a low temperature required for sperm production.
4.3
4.4
Chapter 4
Sperm ducts: They transport sperms from testes to penis.
Accessory sex glands: They produce various substances that nourish the sperm, for example,
prostate gland, seminal vesicles and bulbourethral gland.
Urinary bladder
Seminal
vesicle
Vas deferens
Rectum
Urethra
Penis
Anus
Prostate
F i g . 4 . 4 Male reproductive system
Penis: Penis is the male external genitalia, which transfers and releases urine. It also transfers
semen from the male reproductive tract into the reproductive tract of female during sexual
intercourse.
Semen: Semen is the fluid that contains sperm. Apart from sperms, semen also contains other
substances, like citric acid, free amino acids, fructose, enzymes, prostaglandins, etc., that nourish
the sperm and also make their movement easy.
Sperm: Sperm is the male gamete. It is a single cell with three main parts:
Neck
Middle
piece
Head
Tail
Mitochondrion
Nucleus
Acrosome
F i g . 4 . 5 Structure of sperm
Reproduction in Animals and Plants
1. H
ead: Possesses nucleus and contains a structure called acrosome (which contains hydrolytic enzymes, like acrosin and hyaluronidase), that helps in penetrating female gamete.
2. M
iddle piece: Contains numerous mitochondria which produce energy for the movement of sperm tail and thereby facilitating sperm movement inside the female reproductive
tract, which is essential for fertilization.
3. Tail: Helps in sperm movement inside the female reproductive tract.
Female Reproductive Organs
Female reproductive organs in human include a pair of ovaries, oviducts (fallopian tubes), uterus,
cervix and vagina.
Fallopian tube
Uterine fundus
Uterus
Ovary
Fimbriae
Ovarian ligament
Cervical canal
Cervix
Endometrium
Myometrium
Perimetrium
Vagina
F i g . 4 . 6 Female reproductive system
Ovaries: They produce female gamete that is known as female egg or ovum. There are two
ovaries, right and left ovary. Every month a single matured egg is released from only one of
the ovaries.
Oviduct or fallopian tube: The tube structure present between the ovaries and uterus is called
fallopian tube. Ovum released from ovary reaches uterus through fallopian tube.
Uterus: It is shaped as an inverted pear and is supported by ligaments attached to the pelvis. It is
the site for implantation of the zygote and complete foetal development.
Cervix: Cervix is the lower part of uterus and connects uterus and vagina. The cavity of cervix
is called cervical canal.
Vagina: Vagina is a tube-like structure that extends from the cervix to outside of the body. It is
the site for sperm deposition at the time of coitus. It functions as a way for the menstrual flow
and also as a passage for the baby to come out during vaginal delivery.
4.5
4.6
Chapter 4
Ovum or Egg
The female gamete is known as an ovum or egg. It is spherical in shape. Egg is a single cell and
its size varies depending on the species. For example, the human egg is very small while ostrich
egg is the largest cell.
The release of eggs from the ovaries is called ovulation.
Corona radiata
Follicile cells
Cytoplasm
Nucleus
Plasma membrane
Zona pellucida
F i g . 4 . 7 Structure of ovum
Fertilization
The fusion of male (sperm) and female gamete (ovum) is known as fertilization. During fertilization, nuclei of sperm and ovum fuse to form the zygote, which is the beginning of an
individual. With the fusion of nucleus, the newly formed individual inherits characters of both
parents, that is, mother and father. In humans, fertilization takes place at the fallopian tube.
The sperms that are deposited inside the vagina by the penis during sexual intercourse move
toward the fallopian tube and meet the egg that is released from the ovary after ovulation. The
deposition of semen into the female vagina during copulation is called insemination. A single
ejaculation of semen contains around 300 million sperms, out of which, only one sperm succeeds in fertilizing the egg.
F i g . 4 . 8 Fertilization of ovum by one sperm
Reproduction in Animals and Plants
Types of Fertilization
According to the place of fertilization, whether inside or outside the body. There are two types
of fertilizations:
1. Internal fertilization:
•• Takes place inside the female body.
•• Male gametes are transferred to the body of female.
•• For example, humans, cows, dogs, hens, etc.
2. External fertilization:
•• Fertilization takes place outside the female body.
•• Usually takes place in the aquatic medium where gametes are released into the water.
•• For example, frog, fish, etc.
Development of Zygote to Embryo
Zygote formed after fertilization is a single cell, which then divides repeatedly to form embryo.
Initial cell divisions of zygote take place at the fallopian tube, after which, the embryo
moves to the uterus and gets embedded in the wall of the uterus and this process is called
implantation. To enable implantation, the uterus goes through many changes, one of which
is the increase in thickness of the inner lining of the uterus (endometrium). The embryo
gradually develops inside the uterus and starts forming organs, such as hands, legs, head,
eyes, etc. The nourishment required for the development of foetus is provided by the
mother through the placenta. Placenta is an organ that connects the developing baby and
mother. This structure provides oxygen and nutrients to the baby and also removes wastes
from the baby’s body. The stage of embryo in which all body parts can be identified is called
foetus. Usually it takes around 38 weeks for complete development of the baby inside the
uterus in humans. When the development is complete, mother gives birth to the baby.
Liver
Stomach
Pancreas
Transverse colon
Small intestine
Placenta
Umbillical cord
Cervical (mucus)
Uterus
Urinary bladder
Rectum
F i g . 4 . 9 Human foetus in uterus
4.7
4.8
Chapter 4
Stages of Human Reproduction
The sequence of events leading to fertilization are explained in the form of a flow diagram.
Male
Female
Male gamete (sperm)
Female gamete (ovum)
Fertilization
Zygote
Embryo
Foetus
Delivery
F i g . 4 . 1 0 Sequence of events taking place in human fertilization
Growth and Development in Human beings
Growth is defined as increase in the size and number of the cells. It is a gradual process that could
be divided into following stages.
Infancy
This stage starts as soon as the child is born. It lasts till the age of two years. Growth occurs rapidly
in this stage. The infants learn various activities like sit, stand, walk, etc., in this stage.
Childhood
Generally, this stage ranges from the age of 2 to 12 years. Significant physical changes take place
during childhood. This stage is marked by intellectual and social growth. The growth occurs at
a steady rate.
Adolescence and Puberty
Adolescence meaning ‘to grow up’, is the period of life, where the body undergoes changes that
lead to reproductive maturity. Adolescence begins around the age of 11 and lasts up to 18 or 19
years of age. It is a transitional stage from childhood to adulthood. Puberty is the time when
an individual attains reproductive maturity. Many changes can be seen among children during
puberty. Some of them are listed below:
•• In boys, at puberty the voice box (larynx) can be seen as protruding parts of throat and is
called Adam’s apple.
Reproduction in Animals and Plants
•• Increased activity of sweat and sebaceous gland is the reason why some people get acne and
pimples at puberty.
•• In girls, development of breasts and broadening of hips take place.
BOYS
GIRLS
Voice change
Low pitched voice
High pitched voice
Increase in height
Shoulders become broader
Changes in body shape
Hips become broader
Increased activity of sweat
and sebaceous glands
Testes start producing
sperms
Growth of facial hair
(moustache, beard), hair
on chest, under arms and
in pubic region
Development of
sex organs
Secondary sexual
characters
Ovaries enlarge and
menstruation starts
Growth of hair under arms
and in pubic region
F i g . 4 . 1 1 Changes seen in boys and girls at puberty
Role of Hormones
The various features that appear during puberty are called secondary sex characters. Unlike primary sex characters (development of sex organs), these features do not have direct involvement
in reproduction but they help in distinguishing male from female. They are caused by hormones
released at the time of puberty.
Following are the secondary sexual changes seen in boys:
••
••
••
••
••
External genitalia (penis) increase in length.
Shoulders get broader.
Boys become more muscular.
Hair grows on face (moustache, beard), chest, armpit, pubic regions.
Voice becomes low pitched.
Following are the secondary sexual changes seen in girls:
••
••
••
••
Breast development takes place.
Hips get broader.
Hair grows in armpits and pubic regions.
Voice becomes high pitched.
From the above, it is clear that some of the changes at puberty are common to boys and girls
while some others are unique. The unique changes are due to the changes in hormone released
in boys and girls.
4.9
4.10
Chapter 4
Problems related to adolescence:
Adolescence is marked by significant changes at physical, emotional, sexual and intellectual levels.
Shift from childhood to adolescence is marked by adjustments that may lead to many problems
discussed as follows.
••
••
••
••
One may start to worry about the physical changes in the body.
One may get inquisitive regarding the changes and may seek incorrect sources for answers.
One may get easily offensive or upset due to sudden hormonal changes.
One may get hasty regarding his/her ability to take decisions and challenges.
Hormones in Puberty
Hormones are chemical substances that are released by endocrine glands directly into the blood
stream. The male hormone that is responsible for puberty changes is testosterone whereas in
females it is oestrogen. These are together known as sex hormones.
Glands are organs that produce various substances. They are of two types:
1. E
ndocrine gland: Releases products directly into the blood, for example, pituitary gland,
thyroid gland, testes and ovary, etc.
2. Exocrine gland: Secretes substances onto the outer surface of body through ducts, for
example, sweat glands, mammary glands, lacrimal glands, etc.
The two primary sex hormones (testosterone and oestrogen) are explained below.
1. T
estosterone: It is the primary male sex hormone, playing key role in reproduction and
maintaining secondary sexual characteristics in men. It starts getting released at puberty. It
is responsible for sperm production in men.
2. Oestrogen: It is the primary female sex hormone, produced by the ovaries. It is required
for the normal functioning of female reproductive system and the release of ovum from
ovaries.
Sex hormones are under the control of hormones released from the pituitary gland. It is explained
in the following flow-diagram.
Pituitary gland
(Luteinizing hormone)
Hormones
(Follicle-stimulating hormone)
Testes
Ovary
Testosterone
Oestrogen
Puberty changes
in male
Puberty changes
in female
F i g . 4 . 1 2 Hormonal regulation at the time of puberty
Reproduction in Animals and Plants
4.11
Menstrual Cycle in Females
Menstruation is the periodic shedding of the endometrial lining which comes
out of the vagina in the form of bleeding and is repeated at an interval of
Info Box!
every 28–30 days. The cycle of various events from one menstruation to the
In ovoviviparous animals,
next one is called the menstrual cycle. Usually the release of ovum from ovary
embryo develops inside the
(ovulation) takes place at the middle of the menstrual cycle, that is, on the
eggs and remains in the
mother’s body. Mother does
14th day. During this period, uterus is also getting ready so as to receive the
not provide nutrition to the
egg or released ovum, if it is fertilized. The lining of uterus becomes thick to
embryo, e,g., shark
provide a proper bed for the fertilized egg or zygote. If fertilization occurs,
the fertilized egg develops into a baby (foetus) in the uterus; otherwise, the
uterus sheds off its thick layer along with blood vessel and unfertilized ovum, which results in
bleeding through the vagina. This is called menstruation which generally lasts for 3–5 days.
i
The first menstruation at puberty in a female is called menarche. Menstrual cycle stops at the age
of 45–50 years and this is called menopause. The various events taking place in the menstrual
cycle are represented below:
Mature ovum gets released from ovary (ovulation)
If sexual intercourse has happened, fertilization may
occur in fallopian tube
Fertilization occurs
Development of foetus
inside the uterus
After complete
development, mother
gives birth to young
one
No fertilization
Unfertilized egg reaches uterus
and uterus starts to shed off
Menstrual bleeding (3–5 days)
Another cycle begins
F i g . 4 . 1 3 Cycle of events during a menstrual cycle
Adulthood
At this stage of human growth and development, all the organs have achieved full growth. This
stage occurs from the age of 18.
Old Age
The beginning of this stage differs in people. On an average, the age of 60 marks the onset of old
age. During this phase, bones become brittle and muscles get weak.
4.12
Chapter 4
Viviparous and Oviparous Animals
According to whether the mother lay eggs or give birth to the young ones, there are two types
of animals as listed below.
•• Oviparous: Which lay eggs. Development takes place outside mother’s body.
•• Viviparous: Which give birth to young ones directly. Development takes place inside
mother’s body.
F i g . 4 . 1 4 Oviparous animal—Hen
F i g . 4 . 1 5 Viviparous animal—Cow
Table 4.1 Points of difference between oviparous and viviparous animals
Oviparous animals
Viviparous animals
These animals lay eggs.
They give birth to the young ones.
Embryo development takes place outside the Embryo development takes place within the
mother’s body.
mother’s body.
The fertilized egg covered by hard shell is
laid in a safe place.
Zygote develops into the young one within the
female body.
After a period of incubation, young ones are After reaching certain stages of growth, young
hatched out, for example, hen and lizard.
ones are delivered out, for example,
humans and cows.
Metamorphosis
After the young ones are born or hatched out, there are two scenarios:
i
Info Box!
In insects like silk moths,
metamorphosis is controlled by insect hormones,
whereas in frog it is
controlled by thyroxine, produced by the thyroid gland.
1. Y
oung ones show similarities with adults and all body parts are present at the time of birth itself. These organisms gradually develop into
adults.
2. Younger ones formed are distinct from the adults. They look different and
even lack some of the features that are present in adults. For example, the
young ones of frog look entirely different from the adults. Their development goes through a larval stage.
Reproduction in Animals and Plants
Egg → Larva (Tadpole) → Adult
Eggs
Embryo
Tadpole
Frog
Tadpole with 4 legs
Tadpole with 2 legs
F i g . 4 . 1 6 Metamorphosis in frog
Here, tadpole larva is different from the adult frog. The transformation of larva into adult through
drastic changes is called metamorphosis.
F i g . 4 . 1 7 Metamorphosis in butterfly
4.13
Quick Recap
4.14
Chapter 4
1. Define binary fission. Give an example.
Binary fission is a mode of asexual reproduction in which the parent organism divides into two younger
ones, for example, Amoeba. Reproduction in amoeba involves division of nucleus into two nuclei, followed by division of cytoplasm into two so that each part receives a nucleus.
2. Define fragmentation and give example.
Fragmentation involves breaking of parent body into several fragments and each fragment then develops
into a new organism, for example, starfish.
3. What are hermaphrodites and give example?
Hermaphrodites are organisms that possess both male and female reproductive organs. Both male and
female gametes will be produced in the same organism, for example, earthworm.
4. What are the male gonads and where are they located?
Male gonads are a pair of testes that produce the male gamete, sperm. They also produce male sex hormone, testosterone. Testes are located outside the body inside a sac-like structure called scrotum that helps
to maintain a low temperature required for sperm production.
5. Define oviduct.
Oviduct, also known as fallopian tube is a tube-like structure present between the ovary and uterus.
Ovum released from ovary reaches the uterus through the oviduct.
6. Define fertilization and what are the different types?
Fertilization is the fusion of male and female gametes, that is, sperm and ovum, to form zygote. According to the place of fertilization, whether inside the body or outside, it is of two types: internal fertilization and external fertilization. Fertilization that takes place inside the body is called internal fertilization,
for example, humans and fertilization that takes place outside the body is called external fertilization, for
example, frogs.
7. Define implantation.
The process by which the embryo gets embedded into the uterine wall is called implantation.
8. What is placenta and write its significance?
Organ that connects developing foetus and mother is called placenta. This structure provides oxygen and
nutrients to the baby and also removes wastes from the body of foetus.
9. What is metamorphosis and give one example?
The transformation of larva into an adult through drastic changes is called metamorphosis, for example,
frogs. The development in frogs goes through the larval stage. The development (metamorphosis) can be
represented as:
Egg → Larva (tadpole) → Adult
10. What are secondary sexual characters?
The various features that appear during puberty are called secondary sexual characters. Unlike primary
sexual characters (development of sex organs), these features do not have direct involvement in reproduction but they help in distinguishing males from females. They are caused by hormones released at the time
of puberty, for example, shoulders get broader and voice becomes deeper in boys whereas in girls, hips
get broader and voice becomes high pitched.
Reproduction in Animals and Plants
Reproduction in Plants
Reproduction in plants is the process by which a new plant develops from a parent plant. In
plants, reproduction is of two types:
1. Asexual reproduction
2. Sexual reproduction
Asexual Reproduction
Asexual reproduction is the development of a new plant from plant parts, such as leaf, root, stem,
bud, etc., that is, from vegetative parts. The young ones produced are identical to the parent
plants. The formation or fusion of gametes or fertilization is absent in this mode of reproduction.
This method produces a large number of plants in a short period of time.
Plants reproduce asexually in two ways: spore formation and vegetative propagation.
Spore Formation
In this method, lower plant organisms produce globular structures called sporangia (singular:
sporangium) which contain spores. When sporangia ripe, they burst open to release spores. These
spores are very light and they have a hard protective coat. The spores develop in a same way as
seedlings develop into plants. These method of asexual reproduction is seen in fungi, mosses,
ferns, etc.
Vegetative Propagation
Vegetative propagation can be done in two ways:
1. Natural
2. Artificial
Natural Methods of Vegetative Propagation
Most plants reproduce vegetatively in nature by the help of various parts, like root, stem and
leaves. New plants can grow naturally from either of these parts, and are discussed in the following sections.
Roots
Plants like sweet potato and dahlia can be propagated vegetatively from roots. These roots
contain small buds, which are capable of generating a new plant whenever they are planted in
the soil.
4.15
4.16
Chapter 4
F i g . 4 . 1 8 Tapioca plant is propagated through roots
Stem
New plants can be produced from the stem also. For example, plants, like potato and onion
could be propagated using their underground stem structures called tuber and bulb, respectively. Sugarcane is also an example for plants that could be propagated by planting segments
of stems.
F i g . 4 . 1 9 Plants propagated through stem
Reproduction in Animals and Plants
Leaves
In plants like Bryophyllum, adventitious buds are present on the notched margins of the leaves.
When these buds fall off and come in contact with moist soil, they give rise to new plants.
F i g . 4 . 2 0 Leaf buds of Bryophyllum
Artificial Methods of Vegetative Propagation
Artificial means of vegetative propagation is used for those plants which produce very few seeds
or non-viable seeds. These methods are done artificially for propagation of desired plants in a
short period of time. Some of the examples are given below:
Cutting
Stem cutting is the most common method used in vegetative propagation. It involves cutting a
portion of the stem bearing 1 or more nodes(capable of rooting) from the parent plant. This cutting is then placed in a rooting medium from where the plant either starts growing immediately
or takes some time. Various chemical substances are used for promoting the growth. Examples of
plants propagated by stem cutting include rose, Hibiscus, Salvia, etc.
Parent
plant
Cutting
Cutting
Cut at
slant
Blade
Sand
Soil or
compost
F i g . 4 . 2 1 Stem cutting in a plant
4.17
4.18
Chapter 4
Grafting
It is a technique in which parts of two different plants are connected or united artificially which
later on develops as a single unique plant. For example, root and shoot of two different plants can
be used for grafting. Here the shoot of the plant with superior quality is called scion or graft and
root system of good quality taken for grafting is termed as a stock. Examples of plants propagated
through grafting include apples, citrus, cherries, etc.
Scion
Stock
F i g . 4 . 2 2 Grafting shown in a plant
Layering
Layering is a method used to develop roots on soft stems, while they are still attached to the plant.
In a simple method, the stem is bent down and allowed to touch the soil, and from the point at
which it touches the soil, new roots develop. Layering can also take place naturally. Examples of
plants propagated by layering include Rhododendron, azalea, etc.
Mother plant
Bendi of stem
Bending
cover
Soil co
Formation of new
plant
Development of new
roots
Peg
Holding of stem below
soil
F i g . 4 . 2 3 Layering shown in a plant
Reproduction in Animals and Plants
Plant Tissue Culture
Plant tissue culture involves cultivation or propagation of plants by growing or culturing
plant cells, tissues or organs under controlled conditions in a laboratory. All the nutrients
required for proper growth will be provided artificially. After they have reached a particular
stage of growth, the plantlets are transferred to separate pots or nursery to grow them into
plants. Examples of plants propagated through this technique include tomato, apple, orchids,
etc.
F i g . 4 . 2 4 Small plants formed in the laboratory by tissue culture
Sexual Reproduction in Plants
Most of the higher plants reproduce sexually. Sexual reproduction in flowering plants involves
the fusion of male and female gamete. Flower is the reproductive organ of plants which produces
the gametes.
Structure of Flower
Flower is the attractive part of a plant that is found in various colours, shapes and fragrances. It is
also the reproductive organ of a plant.
Following are the 4 main parts of a flower:
1.
2.
3.
4.
Accessory floral organs that do not
Calyx
Corolla
participate in reproduction
Reproductive parts or
Stamen (Androecium)
Carpel (Gynoecium)
essential floral organs
The individual unit of calyx are called sepals (which are small green colored leaf like structure
which protect the developing bud) and the individual unit of corolla are called petals (which are
brightly colored structures mainly for the attraction of pollinators).
4.19
4.20
Chapter 4
Stigma
Anther
Style
Stament
Petal
Filament
Sepal
Ovule
Receptacle
Pedicel
F i g . 4 . 2 5 Longitudinal section of a flower showing all parts
Stamen or Androecium
Stamen is the male reproductive organ of a flower and male gamete is produced inside the stamen.
Stamen has two parts: Anther and filament
1. A
nther: It is the structure bearing pollen grains located at the top of the filament of stamen.
2. Filament: It is a long stalk like structure that attaches the stamen with flower parts, such
as petal.
Anthers
Stamen
Pollen sacs
Filament
F i g . 4 . 2 6 Parts of stamen
Reproduction in Animals and Plants
Carpel or Gynoecium
Gynoecium is the female reproductive organ of flower and its individual unit is called pistil.
The pistil of a flower consists of the following three parts:
1. Stigma: It is at the tip of the pistil and forms the landing
platform for pollen grains.
2. Style: It is the long, slender stalk which carries pollen grain
from stigma to the ovary.
3. Ovary: This is the main reproductive organ of the flower,
it encloses the unfertilized female gamete and the fertilized
ovule.
Stigma
Style
Ovule
Ovary
F i g . 4 . 2 7 Parts of pistil
Pollination
The transfer of pollen grains from the male anther of a flower to the female stigma is termed
as pollination. As pollen grains cannot move on their own, external agents, such as wind,
water or animals are required for pollination. These are called pollinating agents. According
to the type of pollinating agent bringing about pollination, it is of different types, as described
below:
Pollination
Anemophily
Entomophily
Hydrophily
• Wind pollination or
pollination with the
help of wind
• Insect pollination or
through insects
• Water pollination or
through water
F i g . 4 . 2 8 Types of pollination based on different pollinating agents
Natural Pollination
Natural pollination is of two types:
1. S
elf-pollination: In this process, pollen grains from anthers of a flower are transferred to
the stigma of the same flower, or another flower of the same plant.
2. Cross-pollination: In this process, pollen grains from anther of a flower are transferred to
the stigma of another flower on a different plant but of the same variety. Cross-pollination
can be carried out by various agents which are known as pollinating agents, for example,
insects, water, wind, etc.
•• Pollination by insects: This is the most common method of natural pollination.
Bees, butterflies and other insects sit on the flowers to collect nectar/juice. While
doing so, the pollen grains from the anther get stuck onto the body of these insects.
When these insects visit another flower, pollen grains get deposited on the stigma of
that flower.
4.21
4.22
Chapter 4
Flowers which are pollinated by insects are large, brightly coloured, and often scented;
for example rose, marigold, night jasmine. In order to attract insects their pollen grains
and stigma are usually sticky. For example, strawberry and mustard flower.
F I G . 4 . 2 9 Butterfly sitting on a flower facilitating pollination
•• Pollination by water: This type of pollination occurs in aquatic plants, like Hydrilla
and Vallisneria. Flowers which are pollinated by water are in light weight so that they can
easily float on water surface. These flowers do not produce nectar.
•• Pollination by wind: In this type of pollination, pollen grains are carried by wind and
get deposited on the stigma. So, pollen grains are produced in large quantities so that at
least some have a chance to reach the stigma. Most wind-pollinated flowers are small,
and have dry and light pollen grains which can be easily carried by wind; for example
rice, maize and grass
Artificial Pollination
i
Info Box!
Scientists at the Indian
Botanical Garden in West
Bengal’s Howrah district
have carried out artificial
pollination of the only double coconut tree in India,
which bears the largest seed
known to science.
In this process, two different varieties of plants are selected both with certain required
characteristics, to produce a new variety of plants. This method leads to an increase in
genetic diversity as different flowers will share and combine their genetic information to
create unique offspring.
For example, a plant with disease-resistance property and another with high-yielding property
could be selected. After selecting, they are made to cross-breed by artificial pollination to
produce a new variety of plants which will have characteristics from both the parent plants.
Artificial cross pollination of rice is very common in the field of agriculture.
The three types of pollination are also explained with the help of diagrams, as given below.
Reproduction in Animals and Plants
Male
Flowers
Water
level
Staminate
Flowers
F i g . 4 . 3 0 (a) Anemophily, (b) Entomophily and (c) Hydrophily
Fertilization
The fusion of male and female gametes is called fertilization. During pollination, a large number
of pollen grains are deposited on the stigma of a flower. Pollen grain starts to germinate and forms
a pollen tube downwards to the ovary. The male gamete within the pollen grain reaches the ovary
through pollen tube and fuses with the female gamete to form the zygote. The zygote later on
develops into an embryo which in turn develops into a young plant.
Germinating
pollen grain
Stigma
Style
Pollen tube
Egg cell
Ovary
F i g . 4 . 3 1 Growth of pollen grains leading to fertilization
Seed Formation
Seed formation completes the process of reproduction in plants. Seed is an embryonic plant
enclosed in a seed coat, with some food reserves (in the form of endosperm). Seed is formed
inside the plant structure called fruit.
4.23
Pistillate
Flowers
4.24
Chapter 4
Seed Dispersal
It is the scattering of seeds over a large area so that they find a suitable place for germination.
Dispersal is carried out by different agencies, like wind (Dandelion), water (coconut), animals
(Cocklebur), etc.
Seed Germination
Seed germination is the process by which a new plant grows from the seed. After the seed has
formed, it remains in a dormant state and waits for suitable conditions for germination. When it
is provided with enough water and if temperature is also suitable, it starts germinating first giving
rise to a seedling. The seedling initially attains nutrients from the seed itself, until it has grown
enough to prepare its own food through photosynthesis.
There are two types of seed germination found in nature:
Epigeal germination: In this type of seed germination the cotyledons (seed) emerge out of the
soil. The cotyledons turn green and act as the first leaves of the plant (carry out photosynthesis).
Examples are bean, castor, etc.
F i g . 4 . 3 2 Epigeal germination
Hypogeal germination: In this type of seed germination the cotyledons (seed) remain inside
the soil. They play no role in photosynthesis. Examples are pea, maize, etc.
F i g . 4 . 3 3 Hypogeal germination
4.25
1. Define vegetative propagation.
sexual reproduction in plants is called vegetative propagation. It is the development of new plants from
A
plant parts, such as leaf, root, stem, bud, etc. The younger ones produced are identical to the parent plants.
Large number of plants can be produced in a short period of time through vegetative propagation. It can
be done in two ways: Natural as well as artificial.
2. Write a note on female reproductive structures of a flower.
ynoecium or carpel is the female reproductive structure of a flower and its free unit is called pistil. Pistil
G
comprises three parts known as stigma, style and ovary. Stigma functions as the landing platform for pollen grains. Ovary encloses the ovule where development of female gamete (egg) takes place. The elongated
stalk that connects ovary with stigma is known as style.
3. Define fertilization.
he fusion of male and female gametes is called fertilization. Large numbers of pollen grains are deposited
T
on the stigma of a flower during pollination. Pollen grains start to germinate and form a pollen tube downwards to the ovary. The male gamete within the pollen grain reaches the ovary through the pollen tube and
fuses with the female gamete to form the zygote. The zygote later on develops into an embryo which in turn
develops into a young plant.
4. What is anemophily?
ransfer of pollen grains from anther to stigma (pollination) with the help of wind is called wind pollinaT
tion or anemophily.
5. Define seed.
S eed is an embryonic plant enclosed in a seed coat, with some food reserves. It is formed inside the plant
structure called fruit.
POINTS TO REMEMBER
•• Reproduction is an essential biological process by which an organism gives birth to its
younger ones.
•• Asexual Reproduction is that type of reproduction in which only 1 individual is involved,
it is found in lower plants and animals, example, Binary fission in Amoeba.
•• Sexual reproduction is a kind of reproduction where two parents are involved with fusion of
male and female gametes. It is found in higher plants and animals, for example, Angiosperms
and Humans.
•• The fusion of male and female gametes is called fertilization.
•• Adolescence is the period of life, where the body undergoes changes that lead to reproductive
maturity.
•• Vegetative propagation is the development of new plants from plant parts, such as leaf, root,
stem, bud, etc.
•• Plant tissue culture involves cultivation or propagation of plants by growing or culturing
plant cells, tissues or organs under controlled conditions in a laboratory.
•• The transfer of pollen grains from the male anther of a flower to the female stigma is termed
as pollination.
•• Seed germination is the process by which a new plant grows from the seed.
Quick Recap
Reproduction in Animals and Plants
4.26
Chapter 4
TEST YOUR CONCEPTS
Directions for questions 1 to 30: Fill in the blanks in
each question.
1. The female gamete is called ________.
26. Ovule is located inside the ________.
2. ________ is the male external genitalia.
27. The seedlings take in nutrients initially from
________.
3. Ovum released from ovary reaches uterus through
________.
4. Structure that connects uterus and vagina is
________.
5. ________ is an example for male accessory sex
gland.
28. Seed is enclosed in ________.
29. ________ act as the receiving part for pollen
grains.
30. The long stalk that attaches stamen with the flower
part is ________.
7. Yeast reproduces asexually through ________.
Directions for questions 31 to 64: For each of the following questions, four choices have been provided.
Select the correct alternatives.
8. ________ part of sperm helps in movement.
31. Male sex hormone is produced by
9. Ovum is produced by ________.
(a) Male gonad
(c) Testes
6. ________ is the male sex hormone.
10. ________ is the largest cell.
11. In humans, fertilization takes place at ________.
PRACTICE QUESTIONS
25. The stalk that connects stigma and ovary is
________.
(b) Prostate gland
(d) Both (a) and (c)
32. Scrotum helps to maintain
12. Release of egg from ovaries is called ________.
(a) Low pH
(c) High temperature
13. In hens, fertilization takes place ________ the
body.
33. Which one of the following is a wrong statement?
14. The stage of embryo in which all body parts can
be identified is called ________.
(b)
Sperm production requires a temperature
higher than normal internal temperature.
15. The organisms that lay eggs are ________.
(c)Semen constitutes sperm and also other substances that nourish the sperm.
16. Puberty is the time when an individual attains
________ maturity.
17. The first menstruation at puberty is called
________.
18. In frogs, metamorphosis is controlled by ________.
19. The gland that releases its contents directly into
the blood are called ________.
20. Sweat gland is an example for ________.
21. Pollen grains are produced in ________.
22. The shoot part of the plant that is selected for
grafting is called ________.
23. The method used to develop roots on soft stems is
________.
24. In potato, vegetative propagation can be done
from ________.
(b) Low temperature
(d) High pH
(a) Testes are located outside the body.
(d) Tail of sperm helps in the movement.
34. Match the following:
A
B
C
D
Yeast
Amoeba
Budding
Fragmentation
(a)
(b)
(c)
(d)
A
iv
ii
iv
ii
B
ii
iv
ii
iv
(i) Hydra
(ii) Budding
(iii) Starfish
(iv) Binary fission
C
i
iii
iii
i
D
iii
i
i
iii
35. Which one of the following options are correct.
IIn amoeba, nucleus and cytoplasm divide simultaneously during binary fission.
Reproduction in Animals and Plants
4.27
II
In budding, the new offspring detaches immediately from the parent.
42. To enable implantation, usually the thickness of
inner lining of the uterus
III
In amoeba, cytoplasm divides first followed by
the division of nucleus.
(a) Decreases
(a) I and II
(b) I and IV
(c) III only
(d) IV only
(c) Increases
(d) First decreases and then remains the same.
43. In which of the following organisms, fertilization
is not internal?
36. Head of sperm contains
(a) Humans
(b) Frogs
(a) Nucleus only
(c) Hens
(d) Dogs
(b) Nucleus and mitochondria
(c) Mitochondria and acrosome
44. In a normal healthy person, a single ejaculation
contains around ______ sperms
(d) Nucleus and acrosome
(a) 300 million
(b) 150 billion
37. Ovum from the ovary reaches the uterus through
(c) 150 million
(d) 300 billion
(a) Cervix
(b) Oviduct
45. Sperm fuses with egg at
(c) Fallopian tube
(d) Both (b) and (c)
(a) Fallopian tube
(b) Uterus
38. The part of sperm that contains mitochondria
(c) Cervix
(d) Vagina
(a) Tail
(b) Acrosome
46. Which one of the following is a wrong statement?
(c) Middle piece
(d) Head
(a)Every month ovum will be released from both
ovaries.
39. The part of sperm that helps in the penetration of
ovum is
(a) Acrosome
(b) Nucleus
(b)Ovoviviparous animals do not provide nutrition to the developing embryo.
(c) Tail
(d) Middle piece
(c)In girls, voice becomes high pitched at puberty.
40. Cervix is
(a) Upper part of the uterus
(b) Middle part of the fallopian tube
(c) Lower part of the uterus
(d) Lower part of the fallopian tube
41. Assertion (A): Sexual reproduction involves
fusion of male and female gametes to form embryo
Reason (R): Gamete is a single cell that can fuse
with another gamete of opposite sex
(a)Both A and R are true and R is the correct
explanation for A.
(b)Both A and R are true but R is the not the
correct explanation for A.
(c) A is true and R is false.
(d) A is false and R is true.
(d)Secondary sex characters do not have direct
involvement in reproduction.
47. Identify the word pair relationship.
Frog: ________
Internal fertilization: ________
48. Match the following
A
B
C
D
Frog
Fish
FSH
LH
(a)
(b)
(c)
(d)
A
ii
iii
ii
iv
i
ii
iii
iv
B
iii
iv
iii
iii
C
i
i
iv
ii
Pituitary gland
Metamorphosis
External fertilization
Testes
D
iv
ii
i
i
PRACTICE QUESTIONS
V
In budding, the new offspring detaches after it
is fully matured.
(b) Remains the same
4.28
Chapter 4
49. Usually ovulation takes place on
(c) Stamen and pistil
(a) 14th day
(d) Androecium and gynoecium
(b) Middle of menstrual cycle
55. The unit of androecium is
(c) Towards the end of menstruation cycle
(a) Stamen
(b) Pistil
(d) Both (a) and (b)
(c) Anther
(d) Stigma
50. Identify the word pair relationship
56. Entomophily involves pollination through:
Endocrine gland
: ________
(a) Wind
(b) Water
________ : Sweat gland
(c) Insects
(d) Birds
51. Which one of the following is not a feature of
viviparous animals?
(a) They give birth to young ones.
(a) Layering
(b) Grafting
(b)
Embryo development takes place inside the
female body.
(c) Vegetative propagation
(c) Less embryonic care and protection.
(d) Plant tissue culture
(d)
Provides nutrition to the foetus through
placenta.
58. Match the following
A Sweet potato
B Potato
C Onion
D Scion
52. Assertion (A): Hen comes under oviparous
animals
Reason (R): Oviparous animals give birth to
young ones
(a)Both A and R are true and R is the correct
explanation for A.
PRACTICE QUESTIONS
57. Cultivation or propagation of plants by growing
plant cells in lab is called
(b)Both A and R are true and R is the not the
correct explanation for A.
(c) A is true and R is false
(d) A is false and R is true
53. Assertion (A): Pituitary gland is an exocrine
gland
Reason (R): It releases it secretions directly into
blood
(a)Both A and R are true and R is the correct
explanation for A.
(b)Both A and R are true and R is the not the
correct explanation for A.
(c) A is true and R is false
(d) A is false and R is true
(a)
(b)
(c)
(d)
A
iii
i
iii
ii
B
ii
ii
i
i
C
iv
iii
ii
iv
i
ii
iii
iv
Stem
Bulb
Root
Graft
D
i
iv
iv
iii
59. Which one of the following is a wrong statement?
(a) Layering can take place naturally.
(b) Grafting is used to develop roots on soft stems.
(c) The free unit of carpel is pistil.
(d) Male gamete is produced in anther.
60. Tapioca can be propagated vegetatively using
________.
(a) Stem
(b) Root
(c) Leaves
(d) None of the above
54. The accessory floral parts are
61. In Bryophyllum plant, new plants can be developed
from
(a) Sepal and tepal
(a) Leaves
(b) Stem
(b) Sepal and petal
(c) Root
(d) Bulb
Reproduction in Animals and Plants
64. Assertion (A): Calyx and corolla are known as
accessory floral organs.
Reason (R): Accessory floral organs do not participate directly in reproduction.
62. Identify the word pair relationship
________ : Potato
Bulb
:
4.29
________
63. The root taken for grafting is called
(a)Both A and R are true and R is the correct
explanation for A.
(a) Scion
(b)Both A and R are true but R is the not the
correct explanation for A.
(b) Graft
(c) Stock
(c) A is true and R is false
(d) Both (a) and (b)
(d) A is false and R is true
MASTERING THE CONCEPTS
Knowledge and Understanding
9. What is menstruation?
2. Explain the mode of reproduction in Amoeba.
10. Name the male and female sex hormones in
humans and the organs that produce them.
3. Write a note on the structure of male gamete.
11. Define grafting and write its significance.
4. Write a note on reproduction of hydra.
12. What are the main parts of a flower?
5. Differentiate between oviparous and viviparous
animals.
13. Which is the male reproductive structure in a
flower? Mention about its parts.
6. List out the major secondary sex characters in girls.
14. Explain the method that is used to develop roots
on soft stem.
7. Explain the role of pituitary gland in puberty
changes?
8. Define a gland and what are its different types?
15. What is pollination? Explain any three modes of
pollination.
16. Explain seed germination.
Application and Analysis
1. Complete the table with missing words
Characteristic
Male
Female
(a) Gamete
(b) Gonad
(c) External
genitalia
(d) Motility of
gamete
(e) Location of
gonad
.................
.................
.................
.................
.................
.................
.................
.................
.................
.................
2. Complete the table given below.
Puberty changes
Male
Female
1. Voice change
2. Change in body
shape
3. Sex organs
development
4. Hair growth
............
............
............
............
............
............
............
............
3. Arrange the following events in the correct order.
Foetus
Ovulation
Embryo
Zygote
Delivery
Fertilization
PRACTICE QUESTIONS
1. What is reproduction and what are the different
types?
4.30
Chapter 4
4. Complete the chart with missing words.
(a)
--------- (1) --------
Androecium
-------- (2) ---------
Pistil
------- (3) ---------
Ovary
Male gamete
Female gamete
Fertilization
------- (4) --------
Embryo
(b)
Young plant
Pollen
(Process of transfer of pollen
grains from anther to stigma)
Stigma
PRACTICE QUESTIONS
------- (2) ------
(Tube structure formed
after pollen germination)
Male gamete reaches ovary
Fusion of male and female gamete
Zygote
------ (3) ------Seed
------ (4) -------
Plant
6. A single ejaculation of semen contains around
300 million sperms, whereas fertilization involves
fusion of one male and one female gamete. How is
fusion of more than one sperm avoided?
7. Genetic variation brings the diversity in traits of
individuals of a population. Which one of the selfpollination and cross-pollination could bring more
genetic diversity?
8. A particular flower is brightly coloured and secrete
nectar. The flower also secrete certain smell to
attract insects. What can be inferred about its
mode of pollination?
9. While growing, a seed derives nutrition from
the endosperm. What happens to the mode of
nutrition when the seed has matured to become
a plant?
Anther
------- (1) ------
5. The temperature inside the scrotum is two degrees
less than the normal human body temperature.
What could be the possible reason for this?
Reproduction in Animals and Plants
4.31
1. Ovum or egg
33. (b)
2. Penis
34. (d)
3. Fallopian tube
35. (d)
4. Cervix
36. (d)
5. Prostate gland
37. (d)
6. Testosterone
38. (c)
7. Budding
39. (a)
8. Tail
40. (c)
9. Ovary
41. (d)
10. Ostrich egg
42. (c)
11. Fallopian tube
43. (b)
12. Ovulation
44. (a)
13. Inside the body
45. (a)
14. Foetus
46. (a)
15. Oviparous
47. External fertilization: Human
16. Reproductive
48. (a)
17. Menarche
49. (d)
18. Thyroxine
50. Pituitary gland: Exocrine gland
19. Endocrine gland
51. (c)
20. Exocrine gland
52. (c)
21. Anther
53. (d)
22. Scion
54. (b)
23. Layering
55. (a)
24. Underground stem
56. (c)
25. Style
57. (d)
26. Ovary
58. (c)
27. Seed
59. (b)
28. Seed coat
60. (a)
29. Stigma
61. (a)
30. Filament
62. Tuber, onion
31. (d)
63. (c)
32. (b)
64. (a)
H i n t s a n d E x p l a n at i o n
TEST YOUR CONCEPTS
4.32
Chapter 4
MASTERING THE CONCEPTS
Knowledge and Understanding
1. Reproduction is the biological process by which
an organism gives birth to its young ones. It is
important for the perpetuation of organisms on
earth. It is of two types:
Asexual reproduction: Does not involve fusion
of male and female gametes and usually one parent
is involved. The younger ones produced will be
exactly identical to parents and are called clones.
4. Hydra reproduces asexually through budding.
Budding involves development of a new organism from the buds formed in the parent’s body. In
hydra, a bud develops as an outgrowth that later on
develops into new hydra. New offspring remains
attached to the parent body and detaches only after
it is fully matured.
Sexual reproduction: Involves fusion of male
and female gametes to form zygote, which later on
develops into a new organism. Younger ones produced will not be identical to parents but resemble
both parents.
H i n t s a n d E x p l a n at i o n
2. Amoeba reproduces asexually through binary fission, where parent organism divides to produce two
younger ones. During binary fission, the nucleus
divides first followed by the division of cytoplasm or
body into two, so that each part receives a nucleus.
Parent cell
Nucleus divides Cytoplasm divides
Two daughter cells
Binary
in Amoeba
Binaryfission
fission
in Amoeba
3. Sperm is the male gamete that consists of three
main parts: a head, a middle piece and a tail. Head
possesses nucleus and contains a special structure called acrosome that helps in penetrating the
female gamete. Mitochondria for energy production are located in the middle piece, and the tail
part helps in motility of sperm.
Head
Tail
Mitochondrion
Nucleus
Acrosome
Structure of sperm
Developing
bud
Fully matured
hydra
Detached
young hydra
Budding
in Hydra
Budding
in hydra
5. Oviparous animals Viviparous animals
These animals lay eggs They give birth to
young ones
Embryonic
Embryonic
development takes
development takes
place outside the
place within the
mother’s body
mother’s body
The fertilized egg
Zygote develops into a
covered by hard shell
young one within the
laid in a safe place
female body
After a period of
After reaching certain
incubation, young
stages of growth,
ones are hatched out
young ones are
delivered out
For example, hens
For example., humans
6.
Neck
Middle
piece
Bud
•
Breast development
•• Hips get broader
•• Hair growth in armpits and pubic regions
•• Voice becomes high pitched
7. The puberty changes in males and females are
controlled by male hormone ‘testosterone’ and
female hormone ‘oestrogen’. These sex hormones
are under the control of hormones released from
the pituitary gland which produces two hormones,
namely, luteinizing hormone (LH) and folliclestimulating hormone (FSH). LH acts on the testes
and induces changes in males. Similarly, FSH acts
Reproduction in Animals and Plants
8. Gland is an organ that produces various substances.
They are of two types:
•• Endocrine gland: Releases products directly
into the blood, for example, pituitary gland.
•• Exocrine gland: Secretes substances onto
outer surface of body through ducts, for
example, sweat gland.
9. Menstruation is the bleeding from uterus and is
repeated at an interval of 28–30 days. The cycle of
various events from one menstruation to the next
one is called menstrual cycle. During these events,
the uterus also gets ready so as to receive the egg
or released ovum, if it is fertilized. The uterus
becomes thicker to provide a proper bed for the
fertilized egg or zygote. If fertilization occurs, the
fertilized egg develops into a baby in the uterus;
otherwise; the uterus sheds off its thick layer, along
with blood vessel and unfertilized ovum, which
results in bleeding through the vagina. This is
called menstruation and it lasts for 3–5 days.
10. The male hormone that is responsible for puberty
changes is testosterone whereas in females it is
oestrogen. These are together known as sex hormones. Testosterone is produced by testes whereas
oestrogen is produced by ovaries.
11. Grafting is a method used for artificial vegetative
propagation. It involves joining of parts of two different plants artificially which later develop into a
single unique plant. For example, Root and shoot
of two different plants can be used for grafting.
Here the shoot of the plant with superior quality is
called scion or graft and root system of good quality taken for grafting is termed as stock.
12. The flower has four different parts, such as: calyx,
corolla, androecium and gynoecium. Calyx and
corolla together constitute the accessory floral parts as
they do not participate in reproduction. Androecium
and gynoecium are the essential parts that take part in
reproduction. The units of androecium and gynoecium are stamen and pistil respectively.
13. Stamen is the male reproductive organ of a flower
and male gamete is produced inside the stamen.
Stamen has two parts anther and filament. Pollen
grains carrying male gamete are produced in the
anther. Filament is the long stalk that attaches the
stamen with floral parts, such as petal.
14. Layering is a method used to develop roots on soft
stems, while it is still attached to the plants. In a
simple method, the stem is bent down and allowed
to touch the soil, and from the point at which it
touches the soil, new roots develop. Layering can
also take place naturally.
15. Transfer of pollen grains from anther to stigma is
called pollination. As pollen grains cannot move
by their own, external agents, such as wind, water
or animal are required for pollination. According
to this, pollination can be water pollination called
hydrophily. Pollination through wind is called
anemophily whereas pollination through bees or
insects is called entomophily.
16. Seed germination is the process by which a new
plant grows from the seed. After the seed has
formed, it remains in a dormant state and waits
for suitable conditions for germination. When it is
provided with enough water and if temperature is
also suitable, it starts germinating first giving rise
to a seedling. The seedling initially attains nutrients from the seed itself, until it has grown enough
to prepare its own food through photosynthesis.
Application and Analysis
2.
1.
Characteristic
Male
Female
(a) Gametes
(b) Gonads
(c) External genitalia
(d) Motility of gametes
(e) Location of gonads
Sperm
Testes
Penis
Motile
Outside
the body
Ovum
Ovaries
Vagina
Non-motile
Inside the
body
Puberty
changes
Male
Voice change
Deeper voice High pitched
voice
Shoulders
Hips get
become
broader
broader
Change in
body shape
Female
H i n t s a n d E x p l a n at i o n
on the ovaries and induces production of oestrogen that causes puberty changes in females.
4.33
4.34
Chapter 4
Sex organs
development
Hair growth
Testes start
producing
sperm
Ovaries
enlarge and
menstruation
starts
Hair growth Hair growth
on face,
in armpit and
chest, armpit pubic region
and pubic
regions
3. Ovulation → Fertilization → Zygote → Embryo
→ Foetus → Delivery
4. (a)
(b)
(1) Gynoecium
(2) Stamen
(3) Anther
(4) Zygote
(1) Pollination
(2) Pollen tube
(3) Embryo
(4) Seedling
H i n t s a n d E x p l a n at i o n
5. A pair of testes are the male gonads which produce
male gametes through the process of spermatogen-
esis. This process is affected by high temperatures
(35oC). For spermatogenesis to occur under suitable conditions, temperature inside male gonads
is two degrees less than normal human body
temperature.
6. As soon as one male gamete (sperm) reaches the
ovum and fertilizes it, the fertilized egg releases
certain substances through a series of reaction that
prevent further male gametes to fuse with it.
7. Self-pollination is the transfer of pollen from the
anther to stigma of the same flower, or another
flower on the same plant. Cross-pollination is the
transfer of pollen from the anther of one flower to
the stigma of another flower on a different individual of the same species. Hence, cross-pollination
allows for more genetic diversity in plants.
8. From the features described above, it can be
inferred that the flower is insect-pollinated. Since,
the insects get attracted to colours, smell and nectar, they assist in transfer of pollens.
9. When the seed has matured to become a plant, it
derives nutrition through the process of photosynthesis which happens in the leaves and results in
the formation of carbohydrates.
Chapter
5
microorganisms
and Human
Health
rememBer
Before beginning this chapter, you should be able to:
• Recall the major categories of microorganisms
• Remember the structure, shape and nutrition in common
microorganisms
key Ideas
After completing this chapter, you should be able to:
•
•
•
•
Understand the basic concepts related to microorganisms
Identify useful and harmful microorganisms
Describe immune system and its components
Discuss common human diseases
5.2
Chapter 5
Introduction
The organisms that cannot be seen with the naked eyes and can be viewed only under the
microscope are called microorganisms or microbes. Microbes are diverse and include bacteria,
fungi, protozoa and some algae. Viruses are also microscopic but they are generally considered
as non-living. They reproduce only inside a host cell, which can be bacteria, plants or animals.
There are some microorganisms that are unicellular, that is, they are made up of only one cell, for
example, bacteria, whereas there are some microorganisms that are made up of more than once
cells and are called multicellular microorganisms, for example, moulds.
Microorganisms are broadly divided into four groups: algae, bacteria, fungi and protozoa.
Bacteria
Fungi
Protozoan
Algae
F i g . 5 . 1 Common microorganisms (bacteria, fungi, protozoan, algae)
i
Info Box!
Antonie Van Leeuwenhoek
is called ‘Father of Microbiology’
Microorganisms could be found anywhere in the biosphere, that is, in soil,
oceans, air, hot springs, deserts, etc. They are even present inside the body of
animals. The study of microorganisms is termed as microbiology. Depending
upon their effects on human health, are two types of microbes, namely useful
or harmful.
Microorganisms and Human Health
Microorganisms
Harmful Microorganisms
Useful Microorganisms
Use in
Medicine
Antibiotic
E.g., Penicillin from
Penicillium
Cause
disease
Vaccine
E.g., Rabies vaccine
using Rabies virus
Human
E.g., Common
cold
Spoil
food
Animal
E.g., Rabies
Spoil Cloth
& leather
Plant
E.g., Citrus
canker
Soil
Fertility
Commercial
use
Decomposers
Curd production
E.g., Lactobacillus
Nitrogen fixers
E.g., Rhizobium
Alcohol and Wine production
E.g., Yeast
Baking industry
E.g., Yeast
F i g . 5 . 2 Classification of microorganisms into useful and harmful
Useful microorganisms
There are many microorganisms that are beneficial to human beings. Some of the examples based
on their uses are given below.
Microorganisms in Food Industry
Microorganisms are widely used for the production of curd, bread, alcohol, etc. Curd contains
bacteria called Lactobacillus that convert milk into curd. Yeast can be used in the baking industry
for making breads, pastries, cakes, etc. Yeast can also be used in the large-scale production of alcohol, wine, vinegar (acetic acid), etc. The basis of using yeast in wine production is fermentation.
Fermentation is the process of converting sugar into alcohol.
Table 5.1
Useful microorganisms in food industry
Microorganism
Use
Lactobacillus
Milk production
Yeast
Bread production
Acetobacter malorum (bacteria)
Vinegar production
Gluconacetobacter azotocaptans (bacteria)
Coffee production
5.3
5.4
i
Chapter 5
Info Box!
Chlorella (a green alga) is
taken as a food supplement.
F i g . 5 . 3 Vinegar, produced by the action of bacteria, is used for pickling
Microorganisms in Medicinal Industry
Microorganisms are used to make antibiotics. These antibiotics are used to kill or stop the growth
of other disease-causing microorganisms. A simple example is penicillin. Penicillin can be
obtained from the fungus Penicillium. These antibiotics can be used to cure many diseases that are
caused by microorganisms, (except viral diseases). Microorganisms can also be used in the production of vaccine. A vaccine is a biological preparation that consists of either dead or weakened
microbes. When a vaccine is introduced into the body, the body produces antibodies against the
vaccine, which remains in the body and protects the body from attack by the same microbe in
the future. The common examples are rabies and tuberculosis vaccines.
F i g . 5 . 4 Medical vials containing vaccines
i
Info Box!
Antibodies are the substances produced by the
body to fight against foreign
particles called antigens.
Sir Alexander Fleming was the person who introduced to the world, the greatest
discovery of that time, the antibiotic ‘Penicillin’. It saved the lives of thousands
of soldiers during the second world war. He was awarded the Nobel Prize in
Physiology or Medicine along with Florey and Chain in the year 1945. Florey
and Chain developed processes to produce penicillin in sufficient quantites to
become widely available.
Microorganisms and Human Health
Microorganisms in Agricultural Practices
Microorganisms act as decomposers in the soil that decompose the dead plant and animal wastes.
Decomposition releases organic nutrients to the soil that can be again used up by plants. Microbes
increase soil fertility by fixing atmospheric nitrogen, for example, Rhizobium. This microbe lives in
root nodules of leguminous plants and increases the nitrogen content in the soil.
F i g . 5 . 5 Root nodules of leguminous plants
Microorganisms in Commercial Industries
There are many microbes that are used in the manufacturing or processing of various products
used commercially. For example, there are certain bacteria that are used to manufacture linen.
Red algae produces ‘Algin’ that is used for thickening cosmetics and food products like jelly. Red
algae also produces ‘Agar’ that is used as a solidifying agent in microbial research at a large scale.
Harmful Microorganisms
Besides their several uses, microorganisms also cause some harmful effects on other living organisms. Microorganisms cause a number of diseases in humans, animals and plants. The microorganisms that cause diseases are called pathogens. The most common are viruses that cause common
cold. Microorganisms also cause food spoilage and damage to clothes, leather, etc.
F i g . 5 . 6 Food spoilage caused by bread mold
5.5
5.6
Chapter 5
Table 5.2 Common diseases caused by microorganisms
Microorganism
Disease
Rhinovirus
Common cold
Bordatella pertusis
Whooping cough
Rubeola virus
Measles
Varicella zoster virus
Chicken pox
As microorganisms are everywhere in the biosphere, and some can also cause diseases, it is important to maintain good health.
Human Health and Immunity
Health may be referred to as the well being of an individual in all aspects, that is, physically, mentally and socially. While immunity is the ability of a person to resist infections and remain disease
free.
Immunity are of two types:
1. I nnate immunity: Inborn immunity or immunity that is inherited from parents, for example, skin (prevents entry of foreign invaders).
2. Acquired immunity: Immunity acquired after birth is called acquired immunity or adaptive immunity, for example, Immunity to chickenpox.
Health of an individual depends on many factors. Some of them are given below:
Immunity
Ability of an individual to
resist disease. Any defect to
the immune system or
immunity, makes the
individual prone to diseases
Genetic defect
Inherited defects from
parents
Human Health
Lifestyle
Food habits, exercise,
personal hygiene, proper
sleep, alcohol abuse,
smoking, obesity. all come
under a person's lifestyle.
Environment
Cleanliness of surroundings,
water and air, adequate
housing, safe communities,
proper waste disposal.
F i g . 5 . 7 Factors contributing towards human health
Microorganisms and Human Health
Immune System
Human immune system is composed of a network of cells, tissues, organs that function
together to defend us against infectious microbes (bacteria, virus, etc.). The coordinated
response of the immune system towards any foreign particles is known as immune response.
The white blood cells and the various lymphatic organs constitute the components of
immune system.
Components of Immune System
The immune system forms the first line of defense against foreign particles which seek entry
inside our body. Skin is the first barrier of the immune system which prevents entry of disease
causing microorganisms (pathogens). Upon gaining entry inside a living body, the pathogens
are encountered with various blood cells which specialize in neutralizing and killing pathogens.
These are discussed below in detail:
White Blood Cells
Lymphocytes, monocytes, macrophages, neutrophils, eosinophils and basophils all come under
white blood cells and provide immunity to the body against infectious diseases and foreign
invaders.
Basophil
Neutrophil
Lymphocyte
Eosinophil
Monocyte
F i g . 5 . 8 Types of white blood cells
Organs
Thymus and bone marrow are the primary lymphoid organs where development of lymphocytes
take place whereas spleen, tonsils, lymph vessels and lymph nodes are the secondary lymphoid
organs where immune responses are initiated.
Working of Immune System
Our immune system must be able to differentiate self from non-self. It does so by detecting
certain molecules like proteins that are found on the surface of all cells. It guides itself to ignore its
own or self-proteins at an early stage. An immunogen is a substance that can initiate an immune
response. In many cases, an immunogen is a bacterium, fungus, virus or toxin.
5.7
5.8
Chapter 5
Adenoids
Thymus
Tonsils
Bronchus
associated
lymphoid
tissue
Bone
marrow
Axillary
lymph nodes
Intestine
Spleen
Peyer’s
patches
Inguinal
lymph nodes
Appendix
F i g . 5 . 9 Lymphatic system-showing all lymphoid organs present in the body
Human Diseases
Disease can be referred to as the state of disturbed ease, or being uncomfortable. Disease affects
the proper functioning or structure of body organs or systems. The changes in the body due to
diseases give rise to certain signs and symptoms.
Human diseases
Based on duration
Acute
Short duration
E.g., Common cold
Bacterial
E.g., Cholera
Chronic
Long duration
E.g., Diabetes
Viral
E.g., Polio
Based on cause
Infectious
Caused by
microorganisms
Fungal
E.g., Skin
infections
Protozoan
E.g., Malaria
Non-infectious
Not caused by
microorganisms
Genetic
E.g.,. Cancer
F i g . 5 . 1 0 Types of diseases based on duration and cause
Lifestyle
E.g., Obesity
Microorganisms and Human Health
Type of Diseases
According to the duration of diseases, they can be divided into two types, that is, acute and
chronic. An acute disease is the one in which the symptoms appear suddenly, worsen rapidly
and then disappear as it heals, example, flu or common cold. Whereas a chronic disease is the
one which develops gradually and worsens over a long period of time, example, chronic back
pain.
Table 5.3
Points of difference between acute and chronic diseases
Acute diseases
Chronic diseases
Lasts for a short period often only a few days
Lasts for a long period of time, sometimes
can be life-long
Develops gradually and worsens over time
Affects our normal health, for example,
weight loss, tiredness, etc.
Require extended care or sometimes even
hospitalization.
For example, diabetes
Sudden onset of symptoms and worsen rapidly
Will not have time to cause major effects on
human health if treated in time
Can be cured
For example, common cold
According to whether or not caused by microorganisms, diseases are of two types:
1. Infectious
2. Non-infectious
Infectious Diseases
Following are the characteristics of infectious diseases:
•• Infectious diseases are caused by pathogens, such as bacteria, viruses, fungi and protozoa,
like chicken-pox, TB, etc.
•• Multicellular organisms like worms can also cause infectious diseases like filariasis.
•• Diseases that can spread from one person to another are called communicable
diseases.
•• Diseases that spread through air, water, food, physical contact with patient, sexual contact,
aerosols (sneeze or cough droplets, etc.) also come under infectious diseases.
Non-infectious Diseases
Diseases that are not caused by microorganisms or infectious agents are called non-infectious
diseases. Some of the examples, are:
Genetic diseases: Caused due to abnormalities in DNA, for example, cancer, cystic fibrosis,
sickle cell anemia etc
Lifestyle diseases: Some diseases can be caused by lifestyle habits, like overeating, under
eating, lack of exercise, etc., for example, obesity, nutrient deficiency diseases, high blood
pressure, etc.
5.9
5.10
Chapter 5
F i g . 5 . 1 1 Chicken pox— an infectious disease
Drug and Alcohol Abuse
Abuse of drug and alcohol can have serious consequences on human health. Nowadays, drug
abuse is very common among teenagers who later on get addicted to it.
Smoking: Tobacco is mainly used for smoking and inhaling, tobacco smoke can cause diseases
of heart; lungs, etc.
Alcohol abuse: Excessive alcohol consumption is called alcohol abuse. It can have many ill
effects on human health, such as nutrient deficiency, liver diseases, fertility problems, etc.
Ways to Maintain Proper Health
‘Health is wealth’, hence maintaining proper health is very essential. Some of the measures that
can be taken to maintain proper health are:
•• Healthy food habits:
~~ Eat nutrient-rich food or balanced diet
~~ Avoid junk foods
~~ Include more vegetables, fruits into the diet
~~ Have food that is properly cooked
Healthy Balanced Diet
Rice & Potatoes
Fruit & Vegetable
They are rich in vitamins
and mineral, and the
wholegrain viarieties contain
plenty of fibre.
They contain vitamins
and minerals, and plant
chemicals called
phytochemicals.
Meat, Fish, Eggs & Beans
They provide nutrients that are vital
for health and maintenance of
your body.
Milk & Dairy Foods
Foods & Drinks
They keep bones strong
and prevent high blood pressure.
such as herbs that
contain vitamins, minerals.
F i g . 5 . 1 2 Balanced diet components
Microorganisms and Human Health
5.11
1. What are microorganisms and give examples?
he organisms that cannot be seen with the naked eyes and can be seen only through a microscope are
T
called microorganisms, for example, bacteria, fungi, etc.
2. Generally, viruses are considered as non-living. Give reason.
iruses are microscopic and generally considered as non-living as they can reproduce only inside a host
V
cell, such as bacteria, plants or animals. They do not have an independent existence.
3. Define fermentation.
he process of converting sugar into alcohol is called fermentation. For example, yeast can convert sugar
T
into alcohol and can be used widely for wine production.
4. Define vaccine.
vaccine is a biological preparation that consists of either dead or weakened microbes. When a vaccine
A
is introduced into the body, the body produces antibodies against the vaccine, which remains in the body
and protects the body from attack by the same microbe in the future, for example, rabies vaccine, BCG
vaccine, etc.
5. What are pathogens and give example?
The microorganisms that can cause disease are called pathogens, for example, viruses cause common cold.
Quick Recap
•• Proper exercise: Exercising regularly in any form lowers the risk of various diseases. It also
helps to maintain an active metabolism.
•• Avoid drug and alcohol abuse: Intake of drugs and excessive consumption of alcohol
may lead to adverse health effects, such as liver damage, kidney diseases, neural diseases, etc.
•• Maintain personal and public hygiene
~~ Always keep personal hygiene
~~ Drink boiled water
~~ Do not leave food uncovered
~~ Keep the surroundings clean
~~ Proper waste disposal
•• Control of disease spreading
~~ Diseases spread by mosquitoes can be controlled by avoiding water stagnation, using
mosquito nets, repellents, etc.
~~ Diseases spread by droplets from sneezing or cough can be prevented by using towels to
mask nose while sneezing.
~~ Avoid breeding of flies.
5.12
Chapter 5
POINTS TO REMEMBER
•• The organisms which are too small to be seen by naked eye and are visible only through
microscopes are called microorganisms.
•• The study of microorganisms is termed as microbiology.
•• Microorganisms are widely used for the production of curd, bread, alcohol, antibiotics, etc.
•• Microorganisms can also be harmful and cause a number of diseases in humans, animals and
plants.
•• Health is referred to as the well being of an individual in all aspects, that is, physically,
mentally and socially.
•• Immunity is the ability of an individual to resist diseases.
•• The coordinated response of the immune system towards any foreign particles is known as
an immune response.
•• Diseases that can spread from one person to another are called communicable diseases,
example common cold.
•• Diseases that do not spread from one person to another are called non-communicable
diseases, for example, diabetes.
•• Health can be maintained by following some good habits, such as eating nutrient-rich food
or balanced diet, avoiding junk foods, including more vegetables and fruits into the diet and
exercise.
Microorganisms and Human Health
5.13
TEST YOUR CONCEPTS
1. The study of microorganisms is called ________.
2. The antibiotic penicillin is produced by the fungus
________.
3. The conversion of sugar into alcohol is known as
________.
4. ________ is a bacterium that can fix atmospheric
nitrogen.
5. Immunity to chickenpox is an example for
________ immunity.
6. Common cold is an example for ________ disease.
7. Diseases caused by microorganisms
________.
are called
(c) Lactococcus
(d) None of the above
16. Identify the wrong statement.
A.A vaccine is a biological preparation that contains active or weakend microbe.
B. Polio is an infectious disease caused by bacteria.
C. Cancer is caused due to abnormalities in DNA.
D. Lifestyle habits can cause diseases like obesity.
(a) A only
(b) B and C
(c) C only
(d) A and B
17. Identify the word pair relationship
Cholera
: ________
______
: Viral
8. Polio is caused by ________.
18. Match the following.
9. Diseases that can spread from one person to
another are called ________.
A
B
C
D
10. Genetic diseases arise due to abnormalities in
________.
Directions for questions 11 to 22: For each of the following questions, four choices have been provided.
Select the correct alternatives.
11. Which one of the following is not an infectious
disease?
(a) Cholera
(b) Polio
(c) Malaria
(d) Obesity
12. Select the odd one out
(a) Neutrophils
(b) RBCs
(c) Basophils
(d) Monocytes
13. Which one of the following is not a communicable disease?
(a) Cancer
(b) Common cold
(d) Malaria
(d) Dengue fever
14. Diseases can spread through
(a) Aerosols
(b) Sexual contact
(c) Water
(d) All the above
15. Bacterium that helps in milk curdling is
(a) Lactobacillus
(b) Rhizobium
(a)
(b)
(c)
(d)
Rhizobium
Lactobacillus
Penicillium
Rabies
A
ii
i
ii
i
B
i
iii
iv
ii
i
ii
iii
iv
C
iii
ii
i
iv
Antibiotic
Soil fertility
Vaccine
Milk curdling
D
iv
iv
iii
iii
19. Substances that are produced by the body to fight
against the invader is
(a) Antibiotic
(b) Vaccine
(c) Antibody
(d) Antigen
20. The antibiotic penicillin was discovered by
(a) Alexander Fleming
(b) Ernst Boris Chain
(c) Robert Hooke
(d) Howard Florey
21. Assertion (A): Yeast can be used commercially to
produce alcohol
Reason (R): Yeast can perform fermentation
(a)Both A and R are true and R is the correct
explanation for A.
(b)Both A and R are true and R is the not the
correct explanation for A.
PRACTICE QUESTIONS
Directions for questions 1 to 10: Fill in the blanks in
each question.
5.14
Chapter 5
(c) A is true and R is false
(d) A is false and R is true
22. Assertion (A): Immunity to chickenpox is considered as acquired immunity.
Reason (R): Immunity that is inherited from parents is considered as acquired immunity
(a)Both A and R are true and R is the correct
explanation for A.
(b)Both A and R are true and R is not the correct
explanation for A.
(c) A is true and R is false
(d) A is false and R is true
MASTERING THE CONCEPTS
Knowledge and Understanding
1. Explain the role of microorganisms in improving
soil fertility.
2. Microorganisms can be harmful to humans. Justify
the statement.
3. Define health and what are the different factors
that affect human health?
4. Define immunity and what are the different types?
5. Write down the differences between acute and
chronic diseases.
6. How can we classify diseases based on the cause?
7. Explain the use of microorganisms in medicine.
8. What are various elements in an immune system?
PRACTICE QUESTIONS
Application and Analysis
1. Nivin was observing his mother making wine using
grapes. He saw that she is adding some amount of
yeast into it. What do you think, what will be the
reason for using yeast?
2. How environment affects someone’s health?
3. A virus is living inside its host cell and is able to
survive and reproduce. What happens when the
same virus is removed out of the host cell?
4. Microorganisms like bacteria are reason behind a
number of diseases some of which are even fatal.
Should all microorganisms be considered harmful
for humans?
5. A vaccine comprises the microbes that are able
to cause diseases. How does a vaccine, then, not
cause any harm when it is injected in our body?
6. Why are foreign particles called antigens?
7. Why is immunity to chicken pox an acquired
immunity?
Microorganisms and Human Health
5.15
TEST YOUR CONCEPTS
1. Microbiology
12. (b)
2. Penicillium
13. (a)
3. Fermentation
14. (d)
4. Rhizobium
15. (a)
5. Acquired
16. (d)
6. Acute
17. Bacteria, polio
7. Infectious diseases
18. (c)
8. Virus
19. (c)
9. Communicable diseases
20. (a)
10. DNA
21. (a)
11. (d)
22. (c)
MASTERING THE CONCEPTS
Knowledge and Understanding
2. Along with uses, microorganisms also cause some
harmful effects on other living organisms. There
are microorganisms that cause diseases in humans,
animals and plants. The microorganisms that can
cause disease are called pathogens, for example,
viruses cause common cold. Microorganisms
also cause food spoilage, and damage our clothes,
leather, etc.
3. Health may be referred to as the well-being of an
individual in all aspects, that is, physically, mentally
and socially. Health of an individual depends on
many factors such as,
Immunity
– Ability to resist disease.
Genetic defects –Inherited defects from parents.
Lifestyle
–Food habits, exercise, hygiene,
etc.
Environment
– Cleanliness of water we drink,
air we breath, etc.
4. The ability of an individual to resist disease is
called immunity. Any defect in the immune system
makes the individual prone to disease. Immunity
are of two types – Innate immunity and acquired
immunity. The inborn immunity or immunity
that is inherited from parent is called innate immunity (e.g., skin). Immunity that is acquired after
birth is called acquired immunity (e.g., immunity
to chicken pox).
5. According to the duration, diseases can be classified into acute and chronic diseases. The main
differences are given below.
Acute diseases
Chronic diseases
Last for a short period
Lasts for a long period
of time, sometimes can
be life-long
Develops gradually and
worsens over time
Sudden onset of
symptoms that worsen
rapidly
Will not have time to
cause major effects on
human health if treated
on time
Affects our normal
health, for example,
weight loss, tiredness,
etc.
H i n t s a n d E x p l a n at i o n
1. Microorganisms help to increase soil fertility in
different ways. They act as decomposers in soil by
decomposing the dead plant and animal wastes.
Decomposition releases organic nutrients to the
soil which can be again used up by plants. Microbes
increase soil fertility also by fixing atmospheric
nitrogen, for example, Rhizobium. Rhizobium lives
in root nodules of leguminous plants and increases the
nitrogen content in the soil.
5.16
Chapter 5
Can be cured
Require extended care
or sometimes even
hospitalization.
For example, common For example, diabetes
cold
6. According to the causes of diseases, they can be
classified into two types: Infectious and non-infectious diseases.
Infectious diseases are caused by microorganisms,
such as bacteria, fungi, etc. These could be spread
from one infected person to a healthy person and
are called communicable diseases, for example,
common cold.
Non-infectious diseases are not caused by microorganisms or infectious agents, for example, genetic
diseases, such as cancer and lifestyle diseases like
obesity.
7. In the medical field, the microorganisms can be
used to make two important products, such as
antibiotics and vaccines. Antibiotics are used to
kill or stop the growth of other disease-causing
microorganisms, for example, penicillin from
Penicillium. Microorganisms can also be used in
the production of vaccine. A vaccine is a biological preparation that consists of either dead
or weakend microorganisms. Vaccines provide
immunity to a particular disease, for example,
rabies vaccine gives protection against the rabies
virus.
8. Human immune system includes a network of
cells, tissues, organs that work together to resist
any attack by foreign invaders (bacteria, virus, etc.)
The various components are,
•• White blood cells: Lymphocytes, monocytes,
macrophages, neutrophils, eosinophils and
basophils.
•• Organs: Thymus, bone marrow, spleen and
lymph nodes.
H i n t s a n d E x p l a n at i o n
Application and Analysis
1. Yeast can convert sugar into alcohol through a process called fermentation. Fermentation is a metabolic process that takes place in the absence of
oxygen, in which organic molecules are converted
into acids, gases or alcohol by the action of certain microorganisms, such as yeast. Nivin’s mother
used yeast to perform fermentation and to convert
grape sugar into wine (alcohol).
2. Environment plays a key role in maintaining proper
health. Along with personal hygiene, environmental hygiene is also important. Cleanliness of water
and air and proper waste disposal management are
also necessary for a healthy life. There are many
diseases that can be caused due to unhygienic
environments, such as cholera, polio, etc., so it is
advised to always keep the environment clean.
3. Outside the host cell, a virus is non-living as it is
unable to function and reproduce. A virus gets the
suitable and necessary environment only inside its
host cell for reproduction.
4. No, not all microorganisms are harmful to human
bodies. There are a number of microorganisms
which help human beings either as food supplement or in medicinal industry or in production of
food.
5. Vaccine is a biological preparation of microbes.
However, the microbe is prepared in its weak
state which is unable to cause harm to human
body.
6. Foreign particles are called antigens because our
body is not familiar with their structure and composition. Upon encountering a foreign body,
our body generates molecules (antibody) to fight
against them. Since antigens cause the generation
of antibodies, they are called antigens.
7. Immunity acquired after birth is called acquired
immunity or adaptive immunity. When the causative agent for chicken pox attacks our body for the
first time, we catch disease as our body is unable
to fight against it. But, a subsequent attack of the
same pathogen does not result in the same condition. Our body then fights against the antigen due
to acquired immunity it has developed from the
first attack.
Chapter
6
ecosystem and
Biodiversity
rememBer
Before beginning this chapter, you should be able to:
• Recall the definition of ecosystem and its components
• Remember the different types of terrestrial and aquatic
ecosystem
• Know the harmful effects of pollutants
key Ideas
After completing this chapter, you should be able to:
• Describe the various components of ecosystem
• Understand the concept of food chain and food web
• Explain the various sources and control methods of different
types of pollution
• Understand the concept of biodiversity
• Understand the concept of wildlife and its conservation
6.2
Chapter 6
Introduction
Ecosystem is the functional unit of nature comprising living organisms and non-living things.
Living beings are known as biotic factors and non-living things are known as abiotic factors.
Biotic factors include microbes, insects, plants, animals, etc. Abiotic factors include air, water,
temperature, soil, humidity, sunlight, etc.
Factors of ecosystem
Biotic
(living)
Abiotic
(non-living)
Microbes,
insects, plants,
animals, etc.
Air, water, temperature,
soil, humidity, light, etc.
F i g . 6 . 1 Factors affecting an ecosystem
Components of an ecosystem
In an ecosystem, biotic and abiotic factors interact with each other to meet their necessities. The
components of ecosystem mainly consist of:
Producers → Consumers → Decomposers
Producers
Producers are the organisms that can synthesize their own food. These include green plants that
utilize water and minerals absorbed from the soil, and sunlight trapped by chlorophyll (greencoloured pigment seen in plants) to synthesize their food. This energy in food is used by other
organisms for their requirements. So green plants are called producers in an ecosystem.
Consumers
All animals that cannot synthesize their own food and depend on green plants directly or indirectly for their energy requirements are called consumers.
Consumers are of three types herbivores, carnivores and omnivores.
Consumer
Herbivores
They eat only plants.
E.g., cow, goat, deer, etc.
Carnivores
They eat flesh of other animals.
E.g., tiger, lion, etc.
Omnivores
They eat both plants and
animals. E.g., bear, man, etc.
F i g . 6 . 2 Types of consumers based on their feeding habits
Ecosystem and Biodiversity
Decomposers
Decomposers are organisms that can break down dead and decaying organisms. The primary
decomposers in many ecosystems are fungi.
Food Chain and Food Web
The process of eating and being eaten up in a linear manner is called food chain. In this, one organism eats other organism for its survival. Food chain results in flow of energy from one trophic level
to another. The amount of energy decreases as it flows from lower trophic to higher trophic levels.
Secondary consumer
Tertiary consumer
Primary consumer
Producer
Final consumer
F i g . 6 . 3 A simple grass type food chain
Trophic Levels
It is a step or division of food chain. Number of trophic level is equal to the number of steps in a
food chain. Main fundamental units of trophic levels are producers (which produce energy in the
ecosystem, for example, green plants) and consumers (which either depend directly on producers
or on other animals that depend on producers).
Tertiary consumer
(Secondary carnivore)
Fourth-trophic level
Secondary consumer
(Primary carnivore)
Third-trophic level
Primary consumer
(Herbivore)
Producer
Second-trophic level
First-trophic level
F i g . 6 . 4 Flow diagram showing increasing trophic levels
Interconnected food chain in an ecosystem is called food web. It includes a number of food chains. It
is an important ecological concept. It represents the various feeding relationships within a community.
6.3
6.4
i
Chapter 6
Info Box!
fox
sparrowhawk
A food chain is a linear
sequence of organisms,
whereas food webs consist
of many interconnected
food chains.
blackbird
fieldmouse
rabbit
grass
sparrow
rosehip
berries
slug
blackberries
F I g . 6 . 5 A food web showing interconnected food chains
Biomagnification
Biomagnification is the increase or accumulation in concentration of toxic substances in the
body of organisms at higher trophic levels. Biomagnification is also known as bioamplification,
for example, an insecticide applied to a plant accumulates in a herbivore that feeds on it. This
insecticide then enters different trophic levels through the food chain. The maximum amount of
such toxic chemicals is seen in human beings, placed at the top of food chain. In an aquatic food
chain, maximum DDT is found in fish-eating birds.
Pesticide washed
off crops into
waterways
Pesticide from
water absorbed
by plankton
Fish eat the
plankton and
absorb pesticide
Penguins or other
sea-birds eat the fish
Pesticide interferes
with egg production
F I g . 6 . 6 Biomagnification of pesticides in an aquatic food chain
Ecosystem and Biodiversity
Natural Resources
The term ‘resource’ refers to any source of supply that is kept in reserve. Natural resources are the
resources that are found in nature and are used by the human beings to support and sustain life.
For example, Sun (ultimate source of energy), water, soil, etc.
Natural resources are classified on the basis of their availability and time taken for them to be
replenished. Based on these criteria, natural resource are classified into the following.
1. Renewable resources
2. Non-renewable resources
Renewable Resources
Renewable resources are the ones which get replenished or restocked naturally through natural
cycles within an adequate timeframe. For example, sun, soil, water, wind, wildlife, forest, etc.
F i g . 6 . 7 Renewable resources of energy
Renewable resources are also called perpetual resources or inexhaustible resources because of
their continuous availability and ability to last billions of years. However, certain resources, such
as water and forest, get exhausted if they are exploited too rapidly to be replenished in adequate
time interval through natural cycles.
Non-renewable Resources
Non-renewable resources are the ones which cannot be replenished or restocked within an
adequate timeframe. For example, coal, petroleum, natural gas, etc.
F i g . 6 . 8 Non-renewable resources of energy
Non-renewable resources are called exhaustible resources because they cannot be easily replenished
once they are lost.
6.5
6.6
Chapter 6
Depletion of Natural Resources
Coal and petroleum are formed from the dead remains of plants and animals buried under the
Earth for millions of years. They are still being formed under the Earth, however, the rate of their
formation is significantly low.
As there have been immense technological advancements taking place in the world, a lot of it
comes at the cost of exploiting our natural resources. Increase in population and hence, increase
in demand for resources has put a tremendous pressure on the resources available to us. The rate
at which they are being exploited has reached an alarming level that their restoration within
adequate timeframe is threatened. Moreover, the ever-increasing demand for land has been
leading to excessive deforestation which has further reduced their availability
i
Info Box!
Agriculture is the leading
cause of deforestation.
F i g . 6 . 9 Deforestation of rainforest
Fossil Fuels
Fossil fuels are formed within the Earth’s crust from the buried plants and animals over a period
of millions of years. Fossil fuels include coal, petroleum, natural gas, etc. All of them essentially
contain carbon.
Coal
Coal is a fossil fuel formed from the remains of plants that lived and died about 100–400 million
years ago. All living plants absorb light energy from the sun through photosynthesis. After the
plants die, this energy is released as the plants decay. Under conditions favorable to coal formation,
the decay process is disturbed, preventing the further release of the stored solar energy. Depending
on the carbon content, coal is classified into following types.
•• Anthracite: Contains about 95% carbon.
•• Bituminous: Contains 65–80% carbon.
•• Sub-bituminous: Contains 30–35% carbon
•• Lignite: Contains 25–30% carbon
Ecosystem and Biodiversity
6.7
WATER
100 million years ago
300 million years ago
Rocks & dirts
Death of giant plants.
Dead plants
Coal
Over millions of years, the plants
were buried under water and dirt.
Heat and pressure turned the
dead plants into coal.
F i g . 6 . 1 0 Formation of coal
Uses of Coal
Coal has a number of uses in the industry sector. It was used extensively during industrial
revolution. It is used in steel production, power generation, as a source of steam energy, etc.
Steam
Coal burnt to
make steam
Water
Steam drives
turbine
Turbine
Electricity from
rotates
generator fed to
generator national grid
F i g . 6 . 1 1 Coal-fired power station for electricity generation
Petroleum
The term ‘petroleum’ is derived from combination of two Latin terms: petra
meaning rock and oleum meaning oil. Petroleum is a naturally occurring,
yellow-to-black coloured liquid found beneath the Earth’s surface. Crude oil is
refined to give useful products as mentioned in table.
Table 6.1
i
Products obtained from petroleum refining
Products
Uses
Petroleum gas
Petrol
Kerosene
Diesel
Lubricating oil
Paraffin wax
Bitumen
Fuel for home and industries
Automobile and aviation fuel
Fuel for stoves
Heavy-motor-vehicle and generator fuel
Lubrication
Candles, Vaseline, etc.
Paints and building roads
Info Box!
Crude oil is the Petroleum
in its natural form when first
collected.
6.8
Chapter 6
Gas
20ºC
150ºC
Gasoline
(Petrol)
200ºC
Kerosene
300ºC
Diesel oil
Crude oil
370ºC
Fuel oil
400ºC
Lubrication oil,
Paraffin wax,
asphalt
FURNACE
F i g . 6 . 1 2 Refining of petroleum
Conservation of Fossil Fuels
Given the variety of ways in which fossil fuels are used by humans, they have become indispensable
for our day-to-day life. However, as fossil fuels are non-renewable resources, their conservation is
of urgent need. They can be conserved in the following ways.
••
••
••
••
Using fuel-efficient vehicles like the ones that run on CNG
Use of alternative sources of energy
Use of biogas to generate electricity
Judicial use of electricity
Forests
Forest is a large area that is predominantly occupied by trees. Forests are the lungs of the Earth
and are essential for continuity of life. They are an important renewable resource. However, their
status is threatened due to their depletion at a fast rate. In the section given below, we shall take
a look at importance and conservation of forests.
Importance of Trees
•• We daily make use of chairs to sit, paper to make notes, tissue to clean our hands after a
meal, etc. In most of our activities, we depend on forests in an unthinkable number of ways.
The importance of trees can be realized with the help of following points.
•• The first and foremost need for having forests is the maintenance of oxygen–carbon dioxide
balance. As we know that plants take in carbon dioxide and give us oxygen through the
process of photosynthesis.
•• Plants release water vapours into the atmosphere through the process of transpiration. This
helps in continuous movement of water cycle which helps to maintain optimum level of
water in nature.
•• Trees give us fruits which are an important source of nutrition.
Ecosystem and Biodiversity
•• Forests are home/habitats to an abundant number of biodiversity of plants
and animals
•• Forests act as buffers during natural disasters like floods.
i
6.9
Info Box!
Forests are home to 80%
of the world’s terrestrial
biodiversity.
F i g . 6 . 1 3 Forests are natural home to most of the wildlife
Deforestation
Deforestation is the cutting down of trees at a large scale over a short period of
time. The over-exploitation of forests threatens the ecosystem and humanity as
we heavily depend on forests for most of the ecological services. Following are
the mains causes of deforestation.
••
••
••
••
••
Small- and large-scale agriculture
Mining
Infrastructure
Pulp plantations
Forest fires
i
Info Box!
Half of the world’s tropical
forests have been destroyed
over the last century.
Conservation of Forests
The following methods can be adopted to conserve forests.
•• Afforestation: It is the practice of establishing a forest in an area which did not have any
previous tree cover.
•• Sensible cutting of trees: It is important that trees are cut down judiciously in order to
fulfill human needs. New trees should be planted for the compensation of cut-down trees.
•• Silviculture: It is the execution of controlling the establishment, growth, composition,
health, and quality of forests to meet diverse needs.
•• Awareness: Society should be made aware of the importance of forests and threats associated
with their depletion. Society should be encouraged to make environment-friendly choices.
F i g . 6 . 1 4 Restoring forests by silviculture
6.10
Chapter 6
Pollution
Pollution is any undesirable change in the physical, chemical or biological characteristics of the
environment that affects the living organisms negatively or may create a potential health hazard.
It is the necessary evil arising due to reckless development and the ever growing population.
Substances that cause pollution are called pollutants, for example, human and animal wastes, garbage, dust, sewage waste, radiation, etc.
Pollution is mainly of three types:
1. Air pollution
2. Water pollution
3. Soil pollution
Air Pollution
Air pollution occurs when harmful substances, such as, smoke, dust, fumes, particulates, etc., are
released into the atmosphere. Most of the air pollution occurs due to burning of coal, petrol,
oil, exhaust from vehicles, fumes from factories, industries, brick kilns, etc. Ash from burning
volcanoes, dust from storms and forest fires also contribute to air pollution but to a lesser extent.
Effects of Air pollution
Air pollution is a real problem regarding public health, environmental issues, health conditions
of plants and animals, etc. The smoke released from various sources may combine with dust particles and fog in the atmosphere to form a deadly mixture called smog. Smog is very harmful to
plants and causes asthma and other respiratory allergies in humans. It also causes global warming
(increase in earth’s temperature due to accumulation of CO2 in the atmosphere), acid rain, etc.
F i g . 6 . 1 5 Industrial emissions causing air pollution
i
Info Box!
Acid rain is caused by emissions of sulphur dioxide
and nitrogen oxide. These
gases react with water in the
atmosphere and produce
acids, such as sulphuric acid
and nitric acid, resulting in
acid rain.
Steps to Control Air Pollution
•• Controlling emission from factories, vehicles, etc.
•• Protecting forest that helps in increasing the amount of oxygen in the
atmosphere.
•• Using public transport and reducing usage of personal vehicles.
•• Avoid burning of trash, wastes, etc.
•• Using natural gas instead of coal, wood, kerosene oil for cooking and
heating purposes.
Ecosystem and Biodiversity
•• Installation of devices which reduce the release of pollutants, like filters, electrostatic
precipitators, etc.
Water Pollution
The contamination of water resources, such as lakes, rivers, oceans, ponds, etc., is called water
pollution. This happens when pollutants are directly or indirectly discharged into the water
sources. Sewages from houses, agriculture, industries, etc., are dumped directly into nearby water
sources. People and animal bathing in water sources also make the water polluted. Fertilizers,
pesticides, insecticides, etc., used in agriculture sometimes reach water sources due to rain which
is again a pollutant.
F i g . 6 . 1 6 Trash dumped near river causing water pollution
Effects of Water Pollution
•• Drinking or using polluted water can be harmful to living things. Bathing in polluted water
can cause skin irritation, rashes, etc.
•• Diseases like cholera, diarrhoea, typhoid, etc., spread through contaminated water.
•• Stagnant sewage water becomes breeding places for insects and pests, such as mosquitoes,
fleas, cockroaches, etc., which cause diseases, like dengue, malaria, chikungunya, etc.
Steps to Control Water Pollution
••
••
••
••
Industrial wastewater should be treated well before dumping into water sources.
Waste, whether industrial or domestic, should not be directly thrown into water sources.
Bathing in water sources should be avoided.
Defecating in open places should not be allowed.
Soil Pollution
Dumping wastes in open area can cause soil pollution. It degrades the soil quality and also reduces
its fertility. Wastes can be of any type, such as industrial wastes, domestic wastes, wastes from
slaughter houses, agricultural wastes, etc. Chemical fertilizers and pesticides from agricultural
field which reach the soil as run-off also contribute to soil pollution.
6.11
6.12
Chapter 6
F i g . 6 . 1 7 Soil pollution
Effects of Soil Pollution
•• When wastes are dumped at a particular area, they start decaying and produce foul smell
which destroys the natural beauty of the surroundings and makes living detrimental for
the local people.
•• They become breeding places for disease-causing germs, flies, insects, etc.
•• The soil below also becomes infertile.
•• Non-biodegredable substances like plastic never degrade and remain there for years. Disease
carriers, such as flies, mosquitoes, cockroaches, etc., transfer disease causing pathogens from
the waste to our food. Consuming such food can make a person sick.
Steps to Control Soil Pollution
••
••
••
••
Quick Recap
Dumping wastes in open should be avoided.
Wastes should be categorized as biodegradable and non-biodegredable.
Domestic wastes should be dumped in a compost pit.
Necessary steps should be taken by municipality for waste treatment and disposal management
of localities.
•• Use of plastic bags must be banned and instead paper bags & cloth bags should be used.
1. What are the main components of an ecosystem and why are they called so?
Ecosystem includes living and non-living things that also have their inter-relationship with each other.
The main components of an ecosystem are:
•• Producers: These organisms can produce their own food mainly through photosynthesis. Other
organisms depend either directly or indirectly on the producers.
•• Consumers: These organisms cannot synthesize their own food and depend on producers for food.
•• Decomposers: These organisms are involved in the decomposition of dead and decaying matter in
the ecosystem.
2. State the difference between food chain and food web.
Food chain is a linear sequence of organisms through which energy produced by producers flows from
lower trophic to higher trophic levels. In food chain, each organism occupies different trophic levels.
Food webs include interconnected food chains. The food webs are more realistic representation of energy
transfer in an ecosystem.
6.13
Two examples of food chain are mentioned below:
Energy flows
from grass to
snake through
food chain
Snake
Highest-Trophic level [Top consumer]
Frog
Carnivore [Secondary consumer]
Grasshopper
Herbivore [Primary Consumer]
Grass
Lowest-trophic level (Producer)
Hawk
Grass
Grasshopper
Snake
Spider
Rat
Frog
3. Define pollution. Name any three types of pollution.
he term ‘pollution’ refers to the undesirable changes in the environment due to the introduction of
T
various contaminants. Substances that cause pollution are called pollutants, for example, industrial wastes,
domestic wastes, etc. Soil, air and water are three types of pollution.
4. What are the various control measures to prevent air pollution?
••
••
••
••
Controlling emission from factories, vehicles, etc.
Protecting forest that helps to increase the amount of oxygen in the atmosphere.
Using public transport and reducing usage of personal vehicles.
Avoiding burning of trash, waste, etc.
5. What are the main causes of water pollution?
ater pollution occurs, when wastes from various industries, houses, hospitals, etc., are released into
W
water bodies, such as rivers, lakes, etc., without any treatment. Wastes from industries contain many
chemicals which add to the water bodies. Similarly, wastes from hospitals carry many disease-causing microorganisms (pathogens) that could be harmful to humans. Fertilizers and other chemicals that are used
in agriculture can also cause water pollution.
Quick Recap
Ecosystem and Biodiversity
6.14
Chapter 6
Biodiversity
The term ‘bio’ means ‘life’ and ‘diversity’ means ‘forms’. The term implies the occurrence of different ecosystems, different species, organisms, their interaction with other living and nonliving
forms, etc.
Biodiversity is of three types: Genetic diversity, species diversity and ecological diversity.
1. G
enetic diversity: It is the diversity in number and types of gene and chromosomes present in different species or variation of genes within the same species, for example, India has
many varieties of mangoes and rice.
2. Species diversity: It implies the variety in number and richness of a species in a particular
region, for example, variety of amphibian species are present in Western Ghats.
3. Ecological diversity: It is the variation in ecosystems in a region. Variation can be in both
terrestrial and aquatic ecosystems, for example, desert, tropical rainforests, etc.
i
Info Box!
Species is a group of organisms that have similarities in
character and that can also
interbreed to produce
a fertile offspring. It is the
basic unit of classification
and taxonomy.
Biodiversity Hotspot
A region with significant levels of biodiversity, which is threatened with
destruction, for example, Western Ghats is called biodiversity hotspot. There
are a total of 4 hotspots in India, namely the Western Ghats, the Himalayas, the
Indo-Burma region and the Sundaland.
F i g . 6 . 1 8 The himalayas—a biodiversity hotspot
They include areas with natural ecosystem that are intact and communities associated with hotspots are wild. Such regions are also homes for endemic natural species. Endemic species are those
which are found only in a particular area. For example, Nilgiri tahr, also known as Nilgiri ibex
or simply ibex, is endemic to the Nilgiri hills and the southern parts of western ghats in the states
of Tamil Nadu and Kerala in southern India.
Ecosystem and Biodiversity
F i g . 6 . 1 9 Nilgiri tahr—an endemic species
Threat to Biodiversity
Significant decrease in biodiversity has taken place within the last few decades. Many organisms
that were once abundant have vanished from the earth’s surface. Some of the reasons that could
have caused such massive destruction are given below:
•• Habitat loss: Ruthless cutting down of the trees and destruction of forest for human
necessities have caused loss of habitat of many species.
•• Over-exploitation of species: Whether a plant or an animal reduces its population.
•• Invasion of foreign species: Invasion of some other species or introduction of some new
species for economic use sometimes drives away the local communities.
•• Intensive agriculture: Spread of agriculture to the grasslands, wetlands, etc., destroys the
habitat of many species.
•• Forestry: Growing economically important trees, such as teak, sandalwood, etc., at the cost
of normal forest trees drives away the local forest inhabitants.
•• Co-extinction: When two different species are dependent on each other, extinction of
one would affect the other species, which results in the extinction of other species also. This
is called co-extinction. For example, in host-parasite relationship, if host gets extinct it will
eventually lead to the extinction of parasite also.
•• Natural calamities: Calamities such as earthquakes and tsunamis wipe away many species
at once.
•• Pollution: Is again a major factor responsible for the extinction of many species from earth
as these species are unable to survive in the polluted environment.
Wildlife and its Conservation
Traditionally, wildlife refers to undomesticated animal and plant species that occur in their
natural habitat or are in a state of life in wild. Wildlife resources form an important link in the
survival of human species and maintenance of the ecological balance of nature. It is also an
area of much curiosity, research and interest among naturalists all over the world. Most of the
wildlife habitats are under severe pressure and a large number of wildlife species have become
extinct or are on the verge of extinction, due to the deleterious activities of humans. So finding
and implementing effective means of conservation of wildlife animals is of utmost importance.
6.15
6.16
Chapter 6
Wildlife conservation is the practice of protecting and conserving plant and animal species in
their natural habitat.
There are two main methods to conserve wildlife which are: In situ conservation and ex situ
conservation
In Situ Conservation
It involves preserving wildlife in its natural habitat. A few examples are national parks, sanctuaries
and biosphere reserves in wild regions with plentiful biodiversity which are explained separately
in the following sections.
National Parks
A national park is a reserved area of land under governmental control which is preserved to protect its biodiversity from human exploitation. It provides special protection to single species of
plants or animals that are rare.
For example, Silent Valley National Park in Kerala. This park protects lion-tailed macaques.
Kaziranga National Park in Assam. This park protects one-horned rhinoceros.
F i g . 6 . 2 0 Kaziranga National Park Assam protects one horned rhino
F i g . 6 . 2 1 Lion-tailed monkey is protected in Silent Valley National Park Kerala
Ecosystem and Biodiversity
Sanctuary
A naturally occurring area such as an island that provides protection for species from hunting,
predation or competition. It is a protected area, a geographic territory within which wildlife is
protected. Limited human activities are allowed inside a sanctuary. Examples are Karakoram wildlife sanctuary, Bharatpur bird sanctuary, etc.
F i g . 6 . 2 2 Great egret in Bharatpur bird sanctuary
Biosphere Reserve
A biosphere reserve is a special ecosystem with flora and fauna that requires protection. They are
managed and studied for conserving the biodiversity present in that region and is a biodiversity
hotspot region. At present there are 18 biosphere reserves in India.
F i g . 6 . 2 3 A herd of bisons in a biosphere reserve
6.17
6.18
Chapter 6
Ex Situ Conservation
Ex situ conservation is conserving the components of an ecosystem outside its natural environment or
in an artificially created environment. It involves conservation of not only wild and cultivated species
but genetic species also, for example, gene banks, zoos, aquariums, botanical gardens, etc.
Some examples of ex situ conservation include:
Zoological Garden
Here animals are enclosed and bred in captivity. They are exhibited to public for recreational
purposes, for example, zoological gardens in Kolkata.
F i g . 6 . 2 4 Elephants eating hay in a zoo
Botanical Garden
It is meant for protecting endangered plant species under artificial conditions away from their
natural environment. They are displayed for public for education, scientific and recreational purposes, for example, Indian Botanical Garden, Howrah, West Bengal.
F i g . 6 . 2 5 Different plant species in a botanical garden
6.19
1. What is a biodiversity hotspot? Give one example.
The region having significant levels of biodiversity is called biodiversity hotspot. These regions serve as
homes to a wide variety of organisms including many endemic species. These areas are threatened with
destruction, for example, the Western Ghats.
2. What does it mean by co-extinction?
When two different species are dependent on each other, extinction of one would affect the other species
which results in its extinction. This is called co-extinction. For example, in host--parasite relationship, if
host gets extinct it will eventually lead to the extinction of parasite also.
3. Differentiate between in situ and ex situ conservation methods.
In situ conservation methods include conservation of wildlife in its natural habitat, for example, national
parks, sanctuaries, etc.
Ex situ conservation involves conservation of an organism outside its natural habitat, for example, zoological gardens, botanical gardens, etc.
4. What is genetic diversity?
Genetic diversity is a kind of biodiversity, which shows diversity in number and types of genes, chromosomes present in different species or variations of genes within the same species.
5. Write a brief note on national park with one example.
National park is a reserved area of land under governmental control preserved to protect its biodiversity
from human exploitation. It provides special protection to single species of plants or animals that are rare,
for example, Silent Valley National Park, Kerala protects lion-tailed macaques.
Threatened Species and Red Data Book
IUCN, International Union for Conservation of Nature and Natural Resources took a lead in
focusing our attention towards declining and disappearing species. The names of such organisms
have been given in ‘Red Data Book’ maintained by IUCN. ‘Red’ indicates stop. It includes all
flora and fauna that are on the verge of extinction. According to the IUCN red list, the species
are categorized in terms of their relative risk of extinction.
Extinct: Species that have totally disappeared from the earth’s surface, for example, Passenger
pigeon, Western black rhinoceros, Pyrenean ibex, Tasmanian tiger, etc.
F i g . 6 . 2 6 Passenger pigeon
Endangered: Species with low population numbers and that are in a state of extinction, for
example, Indian tiger, snow leopard, asiatic lion, etc.
Quick Recap
Ecosystem and Biodiversity
6.20
Chapter 6
F i g . 6 . 2 7 Endangered species—Snow leopard, Indian Tiger and Asiatic lion
Vulnerable: Species that are likely to move into the endangered category, for example, yak, olive
ridley turtle, asiatic lion, etc.
Rare species: Species with a small population, thinly scattered which is not yet endangered or
vulnerable but are at risk, for example, blackbuck, lion-tailed macaque, etc.
F i g . 6 . 2 8 Blackbuck
Ecosystem and Biodiversity
6.21
Important Days in Nature Conservation
Table 6.2
List of important dates related to nature conservation
Date
Day
March 21
World Forest day
March 22
World Water day
April 22
World Earth day
June 5
World Environment Day
Oct 3
World Animal Day
Dec 3
World Conservation Day
Dec 29
Biological Diversity Day
Main Organizations Related to Conservation
Greenpeace: It is an international non-governmental organization which provides international
assistance for nature conservation.
IUCN: International Union for Conservation of Nature and Natural Resources
WWF: The Worldwide Fund for nature
1. How does extinct species differ from endangered species?
xtinct species are organisms that have been totally disappeared from the earth’s surface, for example,
E
passenger pigeons. Endangered species are organisms whose number is decreasing and who have low
population numbers. They are in a state of extinction, for example, tigers.
2. H
ow ex situ conservation differs from in situ conservation? Which method is suitable for the
conservation of endangered species?
x situ conservation involves conserving the organisms outside their natural habitat, for example, zoologiE
cal and botanical gardens.
In situ conservation method involves, conservation of organisms in their natural habitat itself, for example,
national parks, biosphere reserves, etc.
Ex situ conservation is most suitable for conservation of endangered species.
3. What is Red Data Book?
he record that keeps the list of all endangered species is called Red Data Book and it is maintained by
T
IUCN.
Quick Recap
MAB: Man and biosphere, under UNESCO helps in establishing and maintaining biosphere
reserves.
6.22
Chapter 6
POINTS TO REMEMBER
•• Ecosystem is the functional unit of nature which consists of organisms and their environment.
•• The ecosystem is made of components, like producers, consumers and decomposers.
•• Pollution is any undesirable change in the physical, chemical and biological component of
environment. It is mainly of three types, i.e., air, water and soil.
•• Biodiversity is the occurrence of different types of ecosystems, different species and their
interaction with other living and non-living forms.
•• Biodiversity is of three types, i.e., genetic, species and ecological diversity.
•• There has been a significant loss to biodiversity in recent times due to various threats, like
habitat loss, overexploitation, pollution, etc.
•• Wildlife refers to undomesticated species of plants and animals that are found in their natural
habitats. Wildlife conservation is the practice of protecting and conserving these species in
their natural habitats.
•• National parks, wildlife sanctuaries and biosphere reserves come under the in situ method
of wildlife conservation.
•• Zoological and botanical gardens come under ex situ method of wildlife conservation.
•• The Red Data Book maintained by IUCN enlists all the threatened and declining species
of the world.
Ecosystem and Biodiversity
6.23
TEST YOUR CONCEPTS
20. The green pigment that traps solar energy during
photosynthesis is
1. Organisms that feed on plants are called ________.
(a) Anthocyanin
(b) Carotenoid
2. Animals that cannot synthesize food and which
depend on other organisms for food are called
________.
(c) Haemoglobin
(d) Chlorophyll
3. ________ is the functional unit of nature.
4. Microbes and insects are included in ________
factors of an ecosystem.
5. Interconnected food chains are called ________.
6. Organisms that feed on both plant and animals are
________.
7. Organisms that feed on dead and decaying matter
are ________.
8. Biomagnification is also known as ________.
9. Substances that cause pollution are ________.
10. Animals that carry disease-causing microbes are
called ________.
11. Kaziranga National Park protects ________.
12. Bharatpur Bird Sanctuary is an example for
________ conservation.
13. Organisms that are found only in a particular area
are called ________.
14. Extinction of a parasite along with extinction of its
specific host is an example of ________
15. Full form of IUCN is ________.
16. World environment day is ________.
17. Species that are likely to move into endangered
category are ________.
18. Passenger pigeon is an example of ________.
21. Organisms that feed on herbivores are
(a) Decomposers
(b) Carnivores
(c) Omnivores
(d) Producers
22. In a food chain, energy flows from
(a) Higher trophic to lower trophic levels.
(b) From consumer to producer.
(c) From lower trophic to higher trophic levels.
(d)From higher to lower trophic levels and vice
versa.
23. The amount of energy ________ from higher trophic to lower trophic levels.
(a) Increases
(b) Decreases
(c) Remains the same
(d) Cannot be predicted
24. Match the following
A.
B.
C.
D.
Gaseous emission
Agricultural wastes
Cholera
Carriers
(a)
(b)
(c)
(d)
A
i
iii
iv
iii
B
iv
iv
iii
iv
C
iii
ii
i
i
i Water pollution
ii Mosquito
iii. Air pollution
iv Soil pollution
D
ii
i
ii
ii
25. Which one of the following is a wrong statement?
(a)
Accumulation of toxic substances increases
from lower trophic to higher trophic levels.
Directions for questions 19 to 35: For each of the following questions, four choices have been provided.
Select the correct alternative.
(b)Energy reduces as it flows from producer to
consumer.
19. Which one of the following is a herbivore?
(c)Energy reduces as it moves from lower trophic
to higher trophic levels.
(a) Man
(b) Deer
(c) Lion
(d) Bear
(d)Energy content will be high in carnivores than
herbivores in a food chain.
PRACTICE QUESTIONS
Directions for questions 1 to 18: Fill in the blanks in
each question.
6.24
Chapter 6
26. Desert and forest are examples of
(a) Genetic diversity
(b) Ecological diversity
(c) Habitat diversity
(d) None of the above
27. Deforestation will result in extinction of many
species due to
(a)
(b)
(c)
(d)
Overexploitation
Co-extinction
Habitat loss
Introduction of exotic species
28. Lion-tailed macaques are protected in
(a)
(b)
(c)
(d)
Zoological garden
Red Data Book
Museum
Botanical garden
32. Match the following.
A. Endangered
species
– (i)
Species that are
likely to move
into endangered
category
– (ii) Species that have
disappeared
– (iii) Species that are
on the verge of
extinction
– (iv) Species that are
thinly distributed
B. Vulnerable
species
C. Extinct species
(a) Silent Valley National Park
(b) Kaziranga National Park
(c) Bharatpur Bird Sanctuary
(d) Satpura National Park
29. Which one of the following is a correct statement?
PRACTICE QUESTIONS
(a)Overexploitation of species helps in increasing
population number of many species.
(b)Silent Valley National Park is an example of
in situ conservation method which conserves
wildlife outside its natural habitat.
(c)Endemic species are organisms that are found
only in a particular area.
(d)Biodiversity refers to genetic and species diversity only.
30. The record that includes all flora and fauna that are
on the verge of extinction is
(a) Blue Data Book
(b) Red Data Book
(c) Green Data Book
(d) None of the above
31. Ex-situ conservation meant for protecting endangered plant species under artificial conditions is
________.
D. Rare species
(a)
(b)
(c)
(d)
A
(iii)
(ii)
(i)
(iii)
B
(ii)
(i)
(iii)
(i)
C
(i)
(iii)
(iv)
(ii)
D
(iv)
(iv)
(ii)
(iv)
33. Match the following
A.
B.
C.
D.
World water day
World animal day
World conservation day
World environment day
(a)
(b)
(c)
(d)
A
(i)
(iii)
(iii)
(ii)
B
(iiii)
(iv)
(iv)
(i)
C
(i)
(ii)
(iii)
(iii)
(i)
(ii)
(iii)
(iv)
June 5
December 3
March 22
October 3
D
(iv)
(i)
(i)
(iv)
34. Write the full form WWF.
35. Biological diversity day is
(a) March 21
(b) December 29
(c) April 22
(d) June 5
Ecosystem and Biodiversity
6.25
MASTERING THE CONCEPTS
Knowledge and Understanding
1. Write a note on biomagnification and give one
example.
7. How deforestation causes species extinction?
8. Explain biodiversity.
2. What is air pollution and what are the major effects
of air pollution on human beings?
3. How carnivores differ from herbivores?
10. Write a note on the significance of wildlife sanctuary.
4. What are the various control methods for soil
pollution?
11. Make a comparison between zoological and
botanical garden
5. What are the various effects of water pollution
and name any three diseases that are caused due to
consumption of polluted water?
12. What are rare species?
6. What are trophic levels and how energy transfer
occurs from one trophic level to other?
14. What does it mean by ex situ conservation methods? Give two examples.
9. Define species.
13. How national park differs from a zoological
garden?
Application and Analysis
3. Write a note on various in situ conservation methods.
4. Describe the various threats to biodiversity.
5. How various species are classified according to
their risk for existence?
6. Is humidity in atmosphere related to the functioning of biotic factors in an ecosystem?
7. In a grass-type food chain, what would be the level
of a fish?
8. Why in an aquatic food chain, maximum DDT is
found in fish-eating birds?
9. How can gases present in the atmosphere cause
acid rain?
10. Does a group of organisms that are similar to each
other but unable to reproduce form species?
PRACTICE QUESTIONS
1. Producers are important for the proper functioning of an ecosystem. Justify the statement.
2. Analyze the food chain given below and answer
the following questions.
Grass → Grasshopper → Small bird → Snake
→ Owl
(a) Which is the primary carnivore?
(b) Which is the top consumer?
(c)Which organism has the highest energy and
the lowest energy content in body?
6.26
Chapter 6
TEST YOUR CONCEPTS
1. Herbivores
17. Vulnerable
2. Consumers
18. Extinct species
3. Ecosystem
19. (b)
4. Biotic
5. Food webs
6. Omnivores
21. (b)
22. (c)
23. (a)
7. Decomposers
24. (d)
8. Bioamplification
25. (d)
9. Pollutants
26. (b)
10. Carriers
11. One-horned rhinoceros
12. In situ
13. Endemic species
14. Co-extinction
15. International Union for Conservation of Nature
and Natural Resources
H i n t s a n d E x p l a n at i o n
20. (d)
16. June 5
27. (c)
28. (a)
29.
30.
31.
32.
33.
34.
35.
(c)
(b)
(d)
(d)
(c)
Worldwide fund for nature
(b)
MASTERING THE CONCEPTS
Knowledge and Understanding
1. Biomagnification can be defined as the accumulation of toxic substances in the body of an organism
as it moves from lower trophic to higher trophic
levels through the food chain. For example, an
insecticide applied to a plant accumulates in the
body of a herbivore, which will in turn accumulate in the body of organisms present in the next
trophic level, that is, carnivores, and in this way
concentration of insecticide will be maximum in
the body of organisms present at the highest trophic level.
2. Pollution of air due to introduction of harmful substances, such as smoke, dust, fumes, etc., is
called air pollution. The pollutants such as poisonous gases reach the human body through respiration. This can cause breathing problems, damage
to lungs and other respiratory organs.
3. Herbivores feed directly on plants for energy
requirements. They are present in the second trophic level of a food chain, where plants or producers
constitute the first trophic level, for example, cows.
Carnivores are organisms that feed on herbivores.
They eat flesh of other animals. for example, tigers.
4. •• Dumping wastes in open should be avoided.
•• Wastes should be categorized as bio-degradable
and non-biodegradable.
•• Domestic waste should be dumped in a compost
pit.
•• Necessary steps should be taken by municipality
for waste treatment and disposal management
of localities.
5. Contamination of water resources (rivers, lakes,
ponds, etc.) through introduction of harmful substances is called water pollution. Drinking or using
polluted water can be harmful to living things.
Ecosystem and Biodiversity
Top Consumer
(Tertiary Consumer)
Carnivore
(Secondary consumer)
Herbivore
(Primary Consumer)
Producer
The energy synthesized by producers reaches
organisms in the next trophic level or herbivores
when they feed on plants. Similarly energy reaches
each trophic level when organisms in one trophic
level are eaten up by organisms in the next trophic
level. Amount of energy decreases as it flows from
lower to higher trophic levels, in other words,
from producer to consumer.
7. Deforestation or ruthless cutting of trees results in
loss of natural habitat of many organisms. Habitat
loss is the major reason for extinction of species.
8. The occurence of a wide variety of organisms on
earth is called biodiversity. Biodiversity refers to
diversity in the ecosystem, species and their interaction with each other, etc.
Biodiversity is of three types:
•• Genetic diversity: It is the diversity in number
and types of genes, chromosomes present in
different species or variation of genes within the
same species.
•• Species diversity: It implies to the variety in
number and richness of a species in a particular
region.
•• Ecological diversity: It is the variation in
ecosystems in a region. Variation can be in both
terrestrial and aquatic ecosystems, for example,
deserts, tropical rainforests, etc.
9. A group of organisms that have similarities in character and that can also interbreed to produce a fertile offspring.
10. Wildlife sanctuaries are a type of in-situ conservation methods where organisms are protected in
their natural habitat. They provide protection of
species from major threats, such as hunting, poaching, killing, etc. These conservation methods prevent the extinction of various species of organisms,
thereby maintaining their number on earth.
11. Botanical and zoological gardens are examples for
ex situ conservation methods where wildlife is protected outside their natural habitat.
In zoological gardens, animals are enclosed and
bred in captivity. They are exhibited to public for
recreational purposes, for example, Zoological
Gardens in Kolkata. Botanical gardens are meant
for protecting endangered plant species under artificial conditions away from their natural habitat.
They are displayed for public education, recreational and scientific purposes, for example, Indian
Botanical Garden, Howrah, West Bengal.
12. Species with a small population and that are thinly
scattered around the world are called rare species.
They are not yet endangered or vulnerable but are
at risk.
13. National park
In situ conservation
method
Conservation in their
natural habitat
Animals (wildlife) are
protected from public
exploitation
For example, Silent
Valley National Park
Zoological park
Ex situ conservation
method
Conservation outside
their natural habitat
Animals are exhibited
to public for
recreational purposes
For example,
Zoological Gardens in
Kolkata
14. Ex situ conservation is conserving the components
of an ecosystem outside its natural environment or
in an artificially created environment.
Ex situ conservation includes:
Zoological gardens
Here animals are enclosed and bred in captivity. They are exhibited to public for recreational
purposes, for example, Zoological Gardens in
Kolkata.
Botanical Garden
It is meant for protecting endangered plant species
under artificial conditions away from their natural
environment. They are displayed to the public for
educational, scientific and recreational purposes,
for example, Indian Botanical Garden, Howrah,
West Bengal.
H i n t s a n d E x p l a n at i o n
Bathing in polluted water can cause skin irritation,
rashes, etc. Cholera, typhoid and diarrhoea spread
through contaminated water.
6. The trophic level refers to the ‘various steps in a
food chain’. The plants or producers of an ecosystem constitute the lowest or first trophic level.
6.27
6.28
Chapter 6
Application and Analysis
1. Producers are the organisms that have the unique
ability to produce food or energy. They produce
their own food mainly through photosynthesis.
Other organisms that cannot synthesize their own
food depend on producers (green plants) either
directly or indirectly for their energy requirements. Thus producers are the ones that make
energy required by all organisms in an ecosystem.
2. (a) Primary carnivore – Small birds
(b) Top consumer – Owl
H i n t s a n d E x p l a n at i o n
(c)Grass will have the highest energy as it is the
producer and owl will have the lowest energy
because energy level decreases as it flows from
the lower trophic level to the higher trophic
level.
3. In situ conservation includes conservation of wildlife in its natural habitat, for example, national
parks, wildlife sanctuaries and biosphere reserves.
National park: Is a reserved area of land under
governmental control preserved to protect its biodiversity from human exploitation. It provides special protection to single species of plants or animals
that are rare. For example, Silent Valley National
Park in Kerala protects lion-tailed macaques and
Kaziranga National Park in Assam protects onehorned rhinoceros.
Sanctuary: It is a naturally occurring area such as
an island that provides protection for species from
hunting, predation or competition. It is a protected area, a geographic territory within which
wildlife is protected. Limited human activities are
allowed inside a sanctuary. For example, Bharatpur
Bird Sanctuary.
Biosphere reserve: A biosphere reserve is a special ecosystem with flora and fauna that requires
protection. They are managed and studied for
conserving the biodiversity present in that region
and is a biodiversity hotspot region.
4. The main reasons for the loss of biodiversity have
been given below:
•• Habitat loss: Ruthless cutting down of the trees
and destruction of forest for human necessities
have caused loss of habitat of many species.
•• Overe-xploitation of species, whether it is a
plant or an animal, reduces its population.
•• Invasion of foreign species: Invasion of some
other species or introduction of some new
species for economic use sometimes drives away
the local communities.
•• Intensive agriculture: Spread of agriculture
to most of the grasslands, wetlands, etc., destroys
the habitat of many species.
•• Forestry: Growing economically important
trees, such as teak, sandalwood, etc., at the cost
of normal forest trees drives away the local forest
inhabitants.
•• Co-extinction: When two different species
are dependent on each other, extinction of one
would affect the other species which results in
its extinction. This is called co-extinction. For
example, in host–parasite relationship, if host
gets extinct it will eventually lead to extinction
of parasite also.
•• Natural calamities, such as earthquake and
tsunami wipe away many species.
•• Pollution: Is again a major factor responsible
for the removal of many species from earth
as these species are unable to survive in the
polluted environment.
5. Extinct: Species that have totally disappeared from
the earth’s surface, for example, passenger pigeon.
Endangered: Species with low population numbers and are in a state of extinction, for example,
Indian tigers.
Vulnerable: Species that are likely to move into
endangered category.
Rare species: Species with a small population,
thinly scattered and which are not yet endangered
or vulnerable but are at risk.
6. Yes, humidity is an integral part of the functioning of the ecosystem. Humidity forms the abiotic
component of an ecosystem. It is directly involved
in shaping the type of vegetation in an ecosystem.
7. In a grass-type food chain, fish have no trophic
level as the energy is transferred from grass to
primary consumer (grasshopper), secondary consumer (frog) to tertiary consumer (snake). Fish
forms part of aquatic ecosystem. Hence, they are
not involved in this type of food chain.
8. DDT sprayed in fields enters the soil. From soil,
it reaches the ground water and when the agri-
Ecosystem and Biodiversity
9. When it rains, the water reacts with the gases present in the atmosphere. This reaction of water with
sulphur and nitrogen oxides results in the formation of acids viz., sulphuric and nitric acids.
10. For a group of organisms to be able to be called
species, they must interbreed with each other to
form fertile offspring.
H i n t s a n d E x p l a n at i o n
culture waste is dumped into water bodies, DDT
enters water resources. DDT cannot get degraded
biologically because of its composition and hence,
it enters food chain. It is absorbed by aquatic
organisms like fish. Fish, in turn, pass on DDT to
the birds that prey on them. Eventually, the organisms which occupy the highest trophic level suffer
the most (fish-eating birds in this case).
6.29
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Chapter
7
Food—production
and Management
reMeMber
Before beginning this chapter, you should be able to:
• Understand the importance of food in our life
• Remember the basics of agricultural practices
• Recall the concept of animal husbandry
key IdeAs
After completing this chapter, you should be able to:
•
•
•
•
Classify crops
Explain various agricultural practices
Understand hybridization and genetic engineering
Understand and describe animal husbandry
7.2
Chapter 7
Introduction
Food is the third most basic need for life, after oxygen and water. Everyone requires food
to perform normal activities of daily living. Agriculture is the practice of production of
food, fibres, and other useful items by the cultivation of plants and animals. The primary
objective of agriculture is the production of food. As human population has been constantly
increasing, there is an increased need for food production. Rearing of animals on a large
scale for fulfilling our needs for food and other products comes under animal husbandry
while development of existing crop varieties to produce new varieties that are much more
advanced in terms of food production and disease resistance, etc., falls under crop improvement. Animal husbandry and crop improvement programmes play a major role in increasing
food production.
Crops
Plants grown at a large scale on a piece of land are called crops. Few examples of crops are
wheat, cereals, etc. Crops are usually grown to produce food at a large scale that could be sold
for money in the market. Some crops are also grown as fodder crops that are used to feed the
animals.
Crops can be classified into three groups according to the season in which they are
cultivated.
Classification of crops
(Based on season)
Rabi
Kharif
• Monsoon crops
• Grown in rainy season
• Planted in July
• Harvested in October
For example, Rice, Maize,
Soybean, etc.
• Winter crops
• Grown in winter season
• Planted in October
• Harvested in March
For example, Wheat,
Linseed, Mustard, etc.
Zaid
• Summer crops
• Grown in summer
season
• Planted in March
• Harvested in June
For example, Watermelon,
musk melon, pumpkin, etc.
F i g . 7 . 1 Classification of crops on the basis of season
Food—Production and Management
Agricultural Practices
Various steps involved in agriculture are collectively known as agricultural practices, which
include:
•• Ploughing
•• Sowing
•• Addition of manure
and fertilizer
••
••
••
••
Preparation of soil
Irrigation
Weeding
Harvesting
Storage
Adding manure
and fertilizer
Sowing
Storage
Harvesting
Irrigation
Weeding
F i g . 7 . 2 An overview of the steps involved in cultivation of a crop
Ploughing
This is the first step in agricultural practices, which includes preparation of soil before sowing.
Ploughing is done to turn or loosen the soil. The soil crumbs formed after ploughing can be broken with the help of a tool called plank. Levelling is also done after ploughing to make a uniform
soil bed for sowing and irrigation. Levelling also prevents soil erosion.
F i g . 7 . 3 Tractor ploughing field for planting crops
Advantages of Ploughing
•• It helps in bringing nutrient-rich soil to the top layer.
•• It helps in removing weeds.
•• It increases the growth of decomposers (microbes) and earthworms which in turn help in
decomposition of plant and animal wastes.
•• It helps the root to penetrate deep into the soil and allows it to breathe easily.
7.3
7.4
Chapter 7
Tools Used for Ploughing the Field
Plough
Hoe
Cultivator
F i g . 7 . 4 Different tools used in ploughing
Sowing
The act of planting seeds is known as sowing. Before sowing, it has to be ensured that the seeds
are of good quality. Sowing bad quality seeds or damaged seeds reduces the yield. Planting the
seeds at uniform distances is also important to avoid overcrowding. This allows plants to get
enough sunlight, nutrients and water.
Different methods of sowing are:
1. Broadcasting: It is scattering of seeds by hand.
2. Drilling: It is the dropping of seeds into the soil with the help of tools like seed drill.
3. Transplanting: In this method, seeds are grown in the nursery first and then planted into
the field at seedling stage.
4. Use of traditional tool: In this the seeds are sowed manually by the help of funnel shaped
tools.
Drilling
Transplanting
Use of traditional tool
F i g . 7 . 5 Different methods of sowing seeds
Addition of Manure and Fertilizers
Plants absorb nutrients from the soil. Continuous cultivation of crops at a particular piece of land
reduces the soil fertility, which needs to be supplied artificially. The major nutrient-supplying
sources are manures and fertilizers.
Manure: Manure is the organic matter formed by the decomposition of plant and animal wastes.
Manure adds humus to the soil.
Fertilizers: Fertilizers are industrially produced chemicals that contain nutrients required by
plants, for example, Nitrogen, Phosphorus, and Potassium (NPK), Urea, etc.
Food—Production and Management
Table 7.1
Points of differences between manure and fertilizers
Manures
Fertilizers
Plant or animal origin
Organic in nature
Natural product
Supply all primary nutrients
Improve soil properties
Chemically synthesized
Inorganic in nature
Artificial product
Supply specific type of nutrients
Have negative effect on soil, reduce soil fertility on prolonged use
Manures and fertilizers are added to the soil to increase its fertility. However there are some natural methods to increase soil fertility. Some of them are discussed below:
Crop rotation: Growing different crops alternatively on a piece of land is called crop rotation.
For example, wheat and leguminous plants could be cultivated alternatively for higher yield.
Wheat requires more nitrogen from the soil. Nitrogen can be replenished naturally by cultivating
legume in the next season. Leguminous plants contain a bacterium called Rhizobium which is
located in the root nodules. These bacteria are capable of fixing atmospheric nitrogen into the
soil thereby increasing the nitrogen content of the soil.
Mixed cropping: Planting two or more crops simultaneously on the same piece of land is called
mixed cropping. Mixed cropping allows the crops to work together, for example, cotton and
groundnut can be grown together for better yield.
Field fallowing: Leaving the land uncultivated for one or more seasons is called field fallowing.
This helps the soil to replenish the nutrients on its own.
Irrigation
The artificial supply of water to the crops at regular intervals is called irrigation. Irrigation is
mainly used in areas where rainfall is irregular or droughts are expected. The sources of irrigated
water are numerous, like groundwater, water from springs or wells, rivers, lakes or even treated
wastewater. All living organisms require water for their normal growth and functioning. Plants
contain nearly 90% water. For a healthy crop, field needs to be watered regularly.
Types of Irrigation
There are different types of irrigation to supply water to the plant. It is important to water the
plants as uniformly as possible, which allows the plants to get the amount of water it needs. The
three different types of irrigation are:
1. Surface irrigation: Water moves across the surface of an agricultural field.
2. Drip irrigation: Water falls drop by drop at the position of roots. This can be the most
efficient method of irrigation in regions with water scarcity. Water wastage is minimized by
utilizing this method.
7.5
7.6
Chapter 7
F i g . 7 . 6 Drip irrigation in a crop field
3. Sprinkler irrigation: It consists of a main pipe to which many pipes with rotating nozzles
on top are attached. The nozzles rotate at regular intervals. When pressurized water flows
through the main pipe, it escapes through the nozzles. Due to this, the water sprinkles on
the crops and it seems as if it is raining. Sprinkled irrigation is helpful on uneven land and
sandy soil.
F i g . 7 . 7 Sprinkler irrigation in a crop field
Weeding
The unwanted plants that grow along with crops naturally are called weeds. It is important
to remove weeds as they will compete with the crops for nutrients, water, sunlight and space.
The removal of weeds is called weeding. Weeding is usually done before the flowering of
weeds.
Food—Production and Management
Following processes are done for carrying out weeding:
•• Manual removal: Uprooting or cutting the weeds close to the ground.
F i g . 7 . 8 Manual removal of weeds
•• Use of weedicides: Chemicals used for weed control are known as weedicides, for
example, 2, 4–D. They do not damage the crops.
•• Ploughing: Ploughing helps to uproot the weeds, causing them to die.
•• Animal grazing: Allowing animals (goats, cows) to feed on weeds.
F i g . 7 . 9 Weedicide being sprayed on a field
Harvesting
The process of gathering the crops after they mature to separate the useful products, such as grains
is called harvesting. Separation of grains from crops includes two steps:
1. T
hreshing: Separation of grain seeds from harvested crop is called threshing. There is a
machine called combine that can be used for both harvesting and threshing.
2. Winnowing: Separation of grains from chaff is called winnowing.
7.7
7.8
Chapter 7
Winnowing
F i g . 7 . 1 0 Methods used in harvesting
Storage
Storage of grains after harvesting is of great importance as it will affect the yield. If they are
not stored properly, there is a chance of loss of grains due to attack by insects, pests, rats or
microorganisms.
Freshly harvested crops
Drying in sunlight
Large scale
Stored in silos or granaries by
spraying chemical insecticides
Small scale
Stored in jute bag or metallic bins
using dried neem leaves or
turmeric
F i g . 7 . 1 1 Steps involved in storage of harvested crops
Different methods to store grains are given below:
•• Before storing, grains should be dried properly in sunlight to reduce moisture content.
If freshly harvested grains are stored without drying, they may get spoilt or attacked by
microorganisms losing their germination capacity.
•• Grains can be stored at a large scale in silos or granaries, by spraying chemical insecticides.
•• On small-scale production, grains can be stored in jute bags or metallic bins. Instead of
chemical insecticides, dried neem leaves or turmeric can be used to repel insects, pests,
etc.
Food—Production and Management
Granaries
7.9
Silos
1. What are crops and how are they classified?
lants that are cultivated at a large scale on a piece of land are called crops. Crops can be classified into
P
three groups according to the season in which they are cultivated.
harif crops: Crops that are grown in rainy seasons are called kharif crops. They are grown in the peK
riod from July to October, for example, rice, maize, etc.
abi crops: Crops that are grown in winter season are called rabi crops. They are usually planted in
R
October and are harvested in March, for example, wheat, linseed, etc.
aid crops: Crops that are grown in summer season are called zaid crops. They are cultivated in the
Z
period of March to June, for example, watermelon, muskmelon, etc.
2. Which is the first step in agricultural practice?
loughing is the first step in agricultural practices. It is done to turn or loosen the soil. Ploughing can be
P
done using tools, such as plough, hoe and cultivator.
3. Define crop rotation.
rowing different crops alternatively on a piece of land is called crop rotation. For example, wheat and
G
leguminous plants can be cultivated alternatively for higher yield. Wheat requires more nitrogen from the
soil. Nitrogen can be replenished naturally by cultivating legume in the next season. Leguminous plants
contain a bacterium called Rhizobium in the root nodules. These bacteria are capable of fixing atmospheric nitrogen into the soil thereby increasing the soil nitrogen content.
4. Define field fallowing.
eaving the land uncultivated for one or more seasons is called field fallowing. This helps the soil to reL
plenish the nutrients on its own.
5. Write the difference between threshing and winnowing.
hreshing is done to separate grain seeds from harvested crop whereas winnowing is done to separate
T
grains from chaff.
Quick Recap
F i g . 7 . 1 2 Large scale storage of grains
7.10
Chapter 7
Plant Improvement Programmes
Plant improvement or crop improvement programmes include, production of desired plant variety that gives better yield, and possesses qualities, such as disease resistance, resistance to climatic
conditions, etc.
Crop variety that has desired quality can be produced by various methods such as:
Hybridization
It is the process of crossing of two dissimilar plants. Hybridization helps to bring qualities of two
parent plants together in the daughter plant. For example, Jaya and Ratna are two rice varieties
that have been developed through hybridization.
F i g . 7 . 1 3 Hybrid cocoa trees
Genetic Engineering
Development of plant varieties expressing the desired agronomic characteristic is the ultimate
goal of a plant breeder. Since traditional methods of plant breeding were not reliable enough
and did not give satisfactory results, a new technology called genetic engineering was introduced
in plant breeding. Genetic engineering is that technique which involves introduction of a gene
(or DNA) that would impart the desired quality to the crop. It does not always involve inserting
DNA from other organisms, plants can also be modified by switching off their own genes, to
produce a particular trait.
F i g . 7 . 1 4 Developing plants through genetic engineering
Food—Production and Management
Animal Husbandry
A branch of agriculture dealing with rearing of animals for their products is called animal husbandry. It includes dairy farming, poultry, pisciculture, etc. Domesticated animals for commercial
purposes are called livestock, for example, cow, sheep, etc.
Animals are domesticated mainly for:
•• Dairy products: Cow and goat
•• Meat: Cattle and chicken
•• Land management: Animal grazing to control weed growth
•• Wool: Sheep
•• Labour: Horse and donkey
Pisciculture
Apiculture
Dairy farming
Animal
Husbandry
Sericulture
Poultry farming
F i g . 7 . 1 5 Various divisions under animal husbandry
Dairy Farming
Management of animals for milk and milk products is called dairy farming. The main domesticated animals for dairy farming are cows, sheeps, buffaloes and goats. The yield of milk mainly
depends upon the breed quality. So it is important to select breed of good quality and also breeds
with disease resistance.
7.11
7.12
Chapter 7
F i g . 7 . 1 6 Cows in a dairy farm
Following are some of the measures that can be taken to increase milk yield:
•• Select good quality breed.
•• Select breed with disease resistance.
•• Take good care of the farm animals by maintaining proper hygiene and by providing them
with good feeds.
•• Maintain proper hygiene while milking, storage and transport of the milk and its products.
•• Regular visits by veterinary doctor.
Poultry Farming
Domesticating birds for their products is called poultry farming, for example, domesticating
chicken for their meat and eggs. Other birds that are domesticated include duck, turkey, geese,
etc. Factors that affect yield in poultry farming are:
••
••
••
••
Selection of disease-free breeds
Proper and safe farm conditions
Proper feed and water
Maintenance of proper hygiene and health of farm birds
F i g . 7 . 1 7 Chickens in a poultry farm
Food—Production and Management
Types of Chickens
Depending on the utility, poultry chicken are classified into two types as follows.
1. Broilers: Chickens that are reared for their meat are called broilers. They are given a
protein-rich diet. They are reared in groups are raised in well-maintained conditions of
surroundings. Once the batch is reared, the whole area is sterilized and made ready for a
new batch/group.
2. Egg-layers: Chickens that are reared for their eggs are called egg-layers. They are bred
in individual cages. They are fed on wheat and other mashed cereals. They are bred on a
sloping floor such that when an egg is laid, it rolls down and easily comes out of the cage
and get collected.
Sericulture
The rearing of silkworm for the production of silk is called sericulture. Sericulture is also called
silk farming. Most widely used silkworm for sericulture is mulberry silkworm Bombyx mori.
F i g . 7 . 1 8 Silkworms feeding on mulberry leaves
Life Cycle of Bombyxmori
Bombyxmori has a short life cycle consisting of four stages described as below.
Egg stage: The female silk moth lays eggs (thousands in number). These eggs are grown under
suitable environment for growth. It takes about 14 days to hatch.
Larval stage: After hatching, larva comes out of the eggs. These larvae are then placed on the
mulberry leaves which are specifically cultivated for this purpose. The larvae feed on mulberry
leaves.
Pupal stage: After five weeks of eating mulberry leaves, larva climbs a twig of the tree and starts
spinning cocoon. Larvae secrete saliva that contains liquid form of the fibre. Larvae spins large
amount of fibre around themselves forming cocoons. Inside cocoons, larvae undergo changes to
form pupa.
Adult stage: Pupa grows inside the cocoon and undergoes changes. It breaks open the cocoon
and emerges as an adult moth. The adult silk moths mate, lay eggs and die within a few days.
7.13
7.14
Chapter 7
Eggs on mulberry
leaves
Adult moth
Life cycle of silk moth
Larva
Pupa
F i g . 7 . 1 9 Life cycle of silk moth
Production of Silk
Cocoons are harvested within 10 days from pupal stage before the pupa emerges. Cocoons are then
put in boiling water. Pupa are killed by boiling water and the silk fibres are loosened. These fibres
are then spun into silk threads. Each silk fibre processed from one cocoon produces a filament.
Apiculture
Rearing of honey bees for the production of honey and bee wax is called apiculture. Honey is a
sweet, edible fluid that has important medicinal values. It contains sugars, minerals, viamins, etc.
Similarly, bee wax is of great industrial importance. It has been used in many cosmetics, ointments, furniture, polishes, etc.
F i g . 7 . 2 0 Working bees on a honeycomb
Food—Production and Management
Pisciculture
Pisciculture is also known as fish farming which includes rearing of fish usually for food.
There are many uses of fish such as:
•• Food: It is an excellent source of protein, vitamins, etc.
•• For controlling diseases: There are some fish like Gambusia that can feed on mosquito
larvae, thereby help in controlling disease spread by mosquito, such as malaria.
F i g . 7 . 2 1 Fishes underwater in a fish farm
Animal Breeding
The term ‘breed’ refers to a group of animals that are similar in most characters, such as appearance, features, size, etc. Producing improved breeds of domesticated animals is called animal
breeding. The factors that are mainly considered for animal breeding are:
•• Increased yield of products, such as milk, meat, egg, wool, etc.
•• Increased quality of products.
•• Increased resistance of animals to diseases.
Animal breeding involves artificially selecting animals of superior quality and allowing them to
mate to produce progeny with improved quality.
Animal Breeding
Inbreeding
Breeding between
animals from same
breed
Out breeding
Breeding between
unrelated animals
Out crossing
Between animals
of same breed
Cross breeding
Between animals
of different breed
F i g . 7 . 2 2 Branches under animal breeding
Interspecific breeding
Between animals of
different species
7.15
7.16
Chapter 7
Deoni
Dairy breeds of
cattle in a box
Hallikar
Khillari
Ponwar
F i g . 7 . 2 3 Indigenous dairy breeds of cattle
Animal breeding can be done in various ways:
•• Inbreeding: Involves mating of superior animals that are from the same breed, for example,
in case of cattle, superior female that can yield more milk can be mated with superior male
from the same breed to get progeny that has qualities of both parents.
•• Outbreeding: Outbreeding involves breeding between unrelated animals.
Outbreeding is of three types:
1. Outcrossing: Breeding between unrelated animals of the same breed.
2. Crossbreeding: Breeding between animals of different breeds.
3. Interspecific breeding: Breeding between animals of different species.
Draught Animals
Draught animals are the ones that are used to carry heavy burden or pull vehicles. For example,
horses, bullock, donkeys, camels, etc. These animals carry and transport people/goods from one
place to another.
••
••
••
••
Elephants are used to transport heavy items like logs of wood.
Donkeys and camels are used for pulling carts.
Bullocks are also used for ploughing in agricultural field.
Horses are also used for riding for recreational purposes
Food—Production and Management
F i g . 7 . 2 4 Bullock cart
Green Revolution
Green revolution refers to increased agricultural production worldwide through the development
of technologies, beginning most markedly in the late 1960’s. Norman Borlaug, who took the
initiative, is known as ‘Father of Green Revolution.’ It involved the introduction of high yielding
varieties of seeds, increased use of fertilizers, etc.
Animal Diseases
As humans, animals are also prone to illness and diseases caused by a number of reasons. Some of
the major diseases are discussed below.
Livestock Diseases
There are various common diseases which cattle suffer from. Some of them are given below.
Disease
Symptom
Anthrax
Cowpox
Rinderpest
Foot-and-mouth disease
Black quarter
High fever, swelling of body parts; this disease is highly infectious
Appearance of nodules on skin
Discharge from eyes and nostrils
Blisters on mouth and feet
Fever, loss of appetite, difficult breathing
Poultry Diseases
The most common diseases that birds suffer from are Fowl pox and Ranikhet disease. Virus
H5N1 causes avian flu and sometimes the infection passes to humans.
Silkworm Diseases
The most common disease affecting silkworms is Pebrine disease (also called pepper disease). It is
caused by Nosema bombycis (a protozoan). Affected larvae have dots on their body and are unable
to produce silk fibre. This disease mainly occurs during rainy and winter season.
7.17
7.18
Chapter 7
Honeybee Diseases
Common diseases affecting honeybees are:
i
Info Box!
Run-offs of fertilizers deplete oxygen dissolved in
water thereby increasing the
ammonia content. As a result, fish do not get enough
oxygen and their gills turn
purplish. This is called ammonia poisoning.
•• American Foulbrood: It is caused by bacterium Paenibacillus larvae. The
bacteria infects the larvae which die before becoming adults.
•• European Foulbrood: It is caused by the bacterium Melissococcusplutonius.
•• Chalk Brood: It is caused by fungus, Ascosphaeraapis. This disease is most
prevalent in spring during which brood area is expanding
Fish Diseases
Poor quality of water and low oxygen content cause diseases in fish. For example, Whirling disease of salmons caused by Myxobolus cerebralis.
Useful Microorganisms
There are certain microorganisms which are used for manufacture or processing of different food
items. There are many species of algae, bacteria and fungi which are commonly used in food
industry. We shall take a look at how food production and management is done with the help of
these organisms.
Algae
There are certain genera of algae which are used in cultivation and production of different food
products.
Algae are a rich source of vitamins and minerals, which makes them suitable as nutritional supplements. Some species of genus Chlorella have more vitamins than many cultivated plants. Members
of the genus Spirulina are rich in β-carotene vitamin B12. Hence, these genrera are used as
nutritive supplements. Algae are also used as a source of natural colours. Pigments, such as chlorophylls, carotenoids and phycobiliproteins, found in algae are used as natural colourant in food
industry.
Agar, obtained from red algae, is a jelly-like substance used as a medium of growth in laboratories
to grow a number of microorganisms.
F i g . 7 . 2 5 Bacteria grown on agar medium
in laboratory
F i g . 7 . 2 6 Chlorella tablets
Food—Production and Management
7.19
Fungi
Various species of fungi are used in processing of food products. The most commonly used fungus
is Baker’s yeast, a unicellular fungus, that is used to make wheat-based products like bread. Yeasts are
also used in making wine and beer by the process of fermentation. Different varieties of cheese are
produced using different species of fungi. Members of the genus Aspergillus niger are used in production of citric acid. Fungi like mushrooms are eaten as food as they are rich in nutrients.
F i g . 7 . 2 7 Bakers’ yeast is used in
F i g . 7 . 2 8 Armillaria mellea—edible
production of bread
mushroom
Bacteria
1. Define hybridization and write its significance.
he process of crossing of two dissimilar plants is called hybridization. It helps in bringing qualities of two
T
parent plants together in the daughter plant. Hybridization can be done to increase the yield by developing improved crop varieties that have disease resistance, resistance to climate conditions, etc.
2. Differentiate between outcrossing and crossbreeding.
utbreeding and crossbreeding, both are done for developing animals with superior qualities. OutcrossO
ing involves breeding between unrelated animals of same breed whereas crossbreeding involves breeding
between animals of different breeds.
3. What is apiculture and why it is done?
earing of honey bees for honey and bee wax is called apiculture. Honey is sweet, edible fluid that has
R
important medicinal values. It contains sugars, minerals, vitamins, etc. Similarly, bee wax is of greater
industrial importance. It has been used in many cosmetics, ointments, furniture, polishes, etc.
Quick Recap
There are many bacteria that are used to process cheese, coffee and tobacco. Acetobacter aceti is
used in production of vinegar. Members of the genus Lactobacillus are used in production of milk
and yogurt.
7.20
Chapter 7
POINTS TO REMEMBER
•• Agriculture is the practice of production of food, fibre and other commercial crops.
•• There are three types of crops based on the type of season they are grown in, viz., Kharif,
Rabi and Zaid.
•• There are a number of steps involved in agricultural practice starting from ploughing,
sowing, addition of manure and fertilizer, irrigation, weeding to harvesting and storage of
cultivated crops.
•• Techniques like hybridization and genetic engineering have increased the crop yield
manifolds and made some varieties disease resistant.
•• Animal husbandry is the branch of agriculture dealing with rearing and maintenance of
animals for their products.
•• Animal husbandry includes sericulture, apiculture, pisciculture, poultry farming and dairy
farming.
•• Animal breeding involves artificial selection of animals of superior characters and their
mating for increasing yield and quality of products obtained from them.
•• Inbreeding and outbreeding are the two types of animal breeding.
Food—Production and Management
7.21
TEST YOUR CONCEPTS
18. Separation of grains from chaff is called
(a) Threshing
(b) Harvesting
1. Mustard is a ________ crop.
(c) Winnowing
(d) Weeding
2. Scattering the seeds by hand is called ________.
19. Identify the word--pair relationship.
3. Organic matter formed by the decomposition of
plant wastes is called ________.
Seed drill
4. The most efficient method of irrigation is
________.
Plough
5. The tool used to break soil crumbs is ________.
6. Zaid crops are grown in ________ season.
7. The bacterium that is capable of performing nitrogen fixation is ________.
8. Planting different crops on the same land simultaneously is called ________.
9. ________ irrigation is helpful in sandy soil.
10. Chemicals that are used to control weeds are called
________.
11. ________ is the widely used silk worm for
sericulture.
12. Pisciculture involves rearing of ________.
13. Sericulture is also called ________.
14. Breeding between animals of same breed is called
________.
15. Domesticated animals for commercial purposes are
called ________.
Directions for questions 16 to 38: For each of the following questions, four choices have been provided.
Select the correct alternative.
16. Grains produced at a large scale can be stored in
(a) Silos
(b) Jute bags
(c) Granaries
(d) Both (a) and (c)
17. Dried leaves can be used to ________
(a) To repel insects
: ________
________ : Breaking of soil crumbs
: ________
20. Match the following
A
B
C
D
2,4, D
Manure
NPK
Sowing
(a)
(b)
(c)
(d)
A
i
iv
i
iv
i
ii
iii
iv
B
ii
ii
iv
i
Organic matter
Transplantation
Fertilizer
Weedicide
C
iii
i
ii
iii
D
iv
iii
iii
ii
21. Which one of the following is not a rabi crop?
(a) Maize
(b) Wheat
(c) Linseed
(d) Mustard
22. Identify the wrong statement.
(a) Fertilizers add humus to the soil.
(b) Manure provides all primary nutrients.
(c) Long-term use of fertilizer reduces soil fertility.
(d)Crop rotation avoids depletion of a particular
nutrient from the soil.
23. In ________ irrigation water falls drops by drop at
the position of roots.
(a) Surface
(b) Drip
(c) Sprinkler
(d) Manual
24. NPK is an example of
(a) Weedicide
(b) Manure
(c) Fertilizer
(d) Insecticide
(b) To control weeds
25. Leaving the land uncultivated for one or more seasons is called
(c) To increase soil fertility
(a) Crop rotation
(b) Inter cropping
(d) None of the above
(c) Field fallowing
(d) Both (a) and (b)
PRACTICE QUESTIONS
Directions for questions 1 to 15: Fill in the blanks in
each question.
7.22
Chapter 7
26. Assertion (A): Maize is a kharif crop
Reason (R): Maize is grown in rainy season
(a)Both A and R are true and R is the correct
explanation for A.
(b)Both A and R are true and R is the not the
correct explanation for A.
(c) A is true and R is false
(d) A is false and R is true
PRACTICE QUESTIONS
27. Assertion (A): Leguminous plants help in increasing the soil fertility
Reason (R): Leguminous plants can perform
nitrogen fixation
(a)Both A and R are true and R is the correct
explanation for A.
(b)Both A and R are true and R is the not the
correct explanation for A.
(c) A is true and R is false
(d) A is false and R is true
28. Assertion (A): Grains should be dried properly
before storing.
Reason (R): Moisture content increases the
chances of spoilage due to micro-organisms.
(a)Both A and R are true and R is the correct
explanation for A.
(b)Both A and R are true and R is the not the
correct explanation for A.
(c) A is true and R is false
(d) A is false and R is true
29. Select the wrongly matched pairs.
(a) Apiculture
– Honey bee
(b) Sericulture
– Fish
(c) Dairy farming
– Milk
(d) Poultry farming
– Meat
30. Breeding between unrelated animals of different
species is called
(a) Intraspecific breeding
(b) Interspecific breeding
(c) Intergeneric breeding
(d) Crossbreeding
31. Ponwar is an example for ________ breed
(a) Chicken
(b) Foreign cow
(c) Indian cow
(d) None of the above
32. Select the mismatch
(a) Bombyx mori
–
(b) Gambusia
–
(c) Hallikar
–
(d) Bee wax
–
Sericulture
Pisciculture
Poultry farming
Cosmetics
33. Genetic engineering involves manipulation in
(a) DNA
(b) RNA
(c) Gamete
(d) Protein
34. Which of the following is a wrong statement?
(a)Animal grazing can be used to control weed
growth.
(b)Fish farming of Gambusia can be used to control the spread of malaria.
(c)
Bombyx mori is the widely used honey bee
variety used for apiculture.
(d)Bee wax can be used in many cosmetics, polishes, etc.
35. Match the following
A. Gambusia
(i)
B. Silk worm
(ii)
C. Sheep
(iii)
D. Khillari
(iv)
(a)
(b)
(c)
(d)
A
(iv)
(ii)
(iii)
(iv)
B
(ii)
(iv)
(ii)
(iii)
C
(i)
(iii)
(i)
(ii)
Cow
Wool
Sericulture
Disease control
D
(iii)
(i)
(iv)
(i)
36. Identify the one which is not used for dairy
farming.
(a) Deoni
(b) Hallikar
(c) Khillari
(d) Bombyx
37. Select the correctly matched pair.
(a)Outbreeding: Breeding between related animals
(b)Crossbreeding: Inbreeding between animals of
same breed
(c)
Outbreeding: Breeding between unrelated
animals of same breed
(d)Inbreeding: Breeding between animals of different breeds
38. Jaya and Ratna are examples of ________ varieties
(a) Maize
(b) Rice
(c) Wheat
(d) Barley
Food—Production and Management
7.23
MASTERING THE CONCEPTS
Knowledge and Understanding
1. Differentiate between rabi and kharif crops.
8. Write a note on sprinkler irrigation.
2. Write which one is the best method for sowing
and give reason.
9. What is weeding and what are the different methods for weeding?
(a) Broadcasting
(b) Drilling
3. Write the significance of ploughing.
4. Differentiate between rabi and zaid crops with one
example.
5. What does it mean by mixed cropping?
6. Differentiate between manures and fertilizers.
7. Growing different crops alternatively can increase
the yield. Justify the statement.
10. Describe the various methods to increase the yield
in dairy farming.
11. What is animal breeding and what is its importance?
12. What are the main factors that affect the yield in
poultry farming?
13. Compare between the various outbreeding methods.
14. Write about the significance of pisciculture.
1. Describe any one method that can increase the
crop yield.
5. Generally, wheat and leguminous plants could be
cultivated alternatively. Why?
2. What kind of precautions should be taken to avoid
loss during storage of grains?
6. How can water waste be minimized during irrigating the field?
7. Why our dried neem leaves or turmeric added to
grains stored in jute bags?
8. Why is rice grown in the period from July to
October?
3. Maintenance of proper hygiene and health can
increase the yield in animal husbandry. Justify the
statement.
4. Why are broilers fed protein-rich diet?
PRACTICE QUESTIONS
Application and Analysis
7.24
Chapter 7
H i n t s a n d E x p l a n at i o n
TEST YOUR CONCEPTS
1. Rabi
20. (d)
2. Broadcasting
21. (a)
3. Manure
22. (a)
4. Drip irrigation
23. (b)
5. Plank
24. (c)
6. Summer season
25. (c)
7. Rhizobium
26. (a)
8. Mixed cropping
27. (c)
9. Sprinkler irrigation
28. (a)
10. Weedicide
29. (b)
11. Bombyx mori
30. (b)
12. Fish
31. (c)
13. Silk farming
32. (c)
14. Inbreeding
33. (a)
15. Livestock
34. (c)
16. (d)
35. (d)
17. (a)
36. (d)
18. (c)
37. (c)
19. Sowing, plank, turning and loosening the soil
38. (b)
MASTERING THE CONCEPTS
Knowledge and Understanding
1. Kharif crops
Monsoon crops
Grown in rainy season
Planted in July
Harvesting in October
For example, rice and
maize
Rabi crops
Winter crops
Grown in winter season
Planted in October
Harvesting in March
For example, wheat
and linseed
2. Sowing using seed drill is more appropriate as
it helps in planting the seeds in uniform depth
and distance. Sowing seeds at uniform distance
prevents overcrowding and sowing seeds at
appropriate depth reduces the damage caused by
birds.
3. Ploughing is done to turn or loosen the soil and
this is the first step followed in agricultural practices. Advantages of ploughing are:
•• Helps in bringing nutrient-rich soil to the top
layer.
•• Helps in removing weeds.
•• Increases the growth of decomposers (microbes)
and earthworms which in turn help in
decomposition of plant and animal wastes.
•• Helps the root to penetrate deep into the soil
and allows it to breathe easily.
Food—Production and Management
5. Planting two or more crops simultaneously on
the same piece of land is called mixed cropping.
Mixed cropping allows the crops to work together,
for example, cotton and groundnut can be grown
together for better yield.
6. Manure is the organic matter formed by the
decomposition of plants and animal wastes whereas
fertilizers are industrially produced chemicals. The
main differences are given below:
Manures
Fertilizers
Plant or animal
origin
Organic in nature
Natural product
Supply all
primary nutrients
Improve soil
properties
Chemically synthesized
Inorganic in nature
Artificial product
Supply specific types of
nutrients
Have negative effect on soil
and reduce soil fertility
7. Growing different crops alternatively on a piece
of land is called crop rotation. For example, wheat
and leguminous plants could be cultivated alternatively for higher yield. Wheat requires more nitrogen from the soil. Nitrogen can be replenished
naturally by cultivating legume in the next season.
Leguminous plants contain a bacterium called
‘Rhizobium’ which is located in the root nodules.
These bacteria are capable of fixing atmospheric
nitrogen into the soil thereby increasing the nitrogen content of the soil.
8. It consists of a main pipe to which many pipes
with rotating nozzles on top are attached. The
nozzles rotate at regular intervals. When pressurized water flows through the main pipe, it escapes
through the nozzles. Due to this, the water sprinkles on the crops and it seems as if it is raining.
Sprinkled irrigation is helpful on uneven land
and sandy soil.
9. The removal of weeds from the field is called
weeding. It is important to remove weeds as they
will compete with the crops for nutrients, water,
sunlight and space.
Methods of weeding:
•• Manual removal: Uprooting or cutting the weeds
close to the ground.
•• Use of weedicides: Chemicals used for weed
control are known as weedicides, for example,
2, 4–D. They do not damage the crops.
•• Ploughing: Ploughing helps in uprooting the
weeds, causing them to die.
•• Animal grazing: Allowing animals (goats, cows)
to feed on weeds.
10. Management of animals for milk and milk products
is called dairy farming. The animals that are mainly
domesticated are—cows, sheeps, buffaloes and goats.
The yield can be increased by the following methods:
•• Select good quality breed.
•• Select breed with disease resistance.
•• Take good care of the farm animals by
maintaining proper hygiene and by providing
them with good feed.
•• Maintain proper hygiene while milking, storage
and transport of the milk and its products.
•• Regular visits by veterinary doctor.
11. Producing improved breeds of domesticated animals are called animal breeding. Animal breeding
is done to develop improved animal varieties that
have superior qualities, such as disease resistance,
improved yield, improved product quality, etc.
12. Factors that affect yield in poultry farming are:
••
••
••
••
Selection of disease-free breeds
Proper and safe farm conditions
Proper feed and water
Maintenance of proper hygiene and health of
farm birds
13. Breeding between unrelated animals is called outbreeding. It can be done in three ways: Outcrossing,
crossbreeding and interspecific breeding.
Outcrossing
Crossbreeding
Interspecific
breeding
Breeding
between
animals of
same breed
Breeding
between animals
of different
breeds
Breeding
between
animals of
different
species
H i n t s a n d E x p l a n at i o n
4. Rabi crops
Zaid crops
Winter crops
Summer crops
Grown in winter season Grown in summer
season
Planted in October
Planted in March
Harvested in March
Harvested in June
For example,
For example,
wheat, linseed, mustard, watermelon, musk
etc.
melon, etc.
7.25
7.26
Chapter 7
14. Rearing of fish or fish farming is called pisciculture. It is mainly done for two purposes:
•• Food – as they are excellent source of protein,
vitamin, etc.
•• Farming of fish such as Gambusia is also done
as it can feed on mosquito larva and thus can
control diseases spread by mosquitoes.
H i n t s a n d E x p l a n at i o n
Application and Analysis
1. Crop rotation is a method for naturally replenishing nutrients in the soil. It involves growing different crops alternatively.
For example, wheat and leguminous plants could
be cultivated alternatively for higher yield. Wheat
requires more nitrogen from the soil. Nitrogen can
be replenished naturally by cultivating legume in
the next season. Leguminous plants contain a bacterium called Rhizobium which is located in the
root nodules. These bacteria are capable of fixing
atmospheric nitrogen into the soil thereby increasing the nitrogen content of the soil.
2. Storage of grains after harvesting is of great
importance as it will affect the yield. If the grains
are not stored properly, there is a chance of their
loss due to attack by insects, pests, rats or microorganisms. Before storing, grains should be dried
properly in the sunlight to reduce moisture content. If freshly harvested grains are stored without
drying, they may get spoilt or attacked by microorganisms losing their germination capacity.
Insecticides are also utilized to repel insects while
storing. Chemical insecticides are used while
storing grains in silos or granaries. Insecticides of
biological origin such as turmeric or neem leaves
can be used in small-scale storages, such as storage
in jute bags or metallic bins. Suitable temperature
and hygienic conditions are also maintained in
storage areas.
3. Maintenance of proper hygiene will help to keep
the animals healthy and disease free. It will help to
reduce mortality rate. Proper hygiene in the housing, product transport facilities, etc. will in turn
increase the quality of products.
4. Broilers are raised for meat production. Hence,
they are given protein-rich diet so that they are
grown healthy. They are grown to suitable health
and size to produce a quality product for the
consumers.
5. Wheat and leguminous plants could be cultivated
alternatively for higher yield. Wheat requires more
nitrogen from the soil. Nitrogen can be replenished naturally by cultivating legume in the next
season. Leguminous plants contain a bacterium
called Rhizobium which is located in the root nodules. These bacteria are capable of fixing atmospheric nitrogen into the soil thereby increasing
the nitrogen content of the soil.
6. Water waste can be minimized during irrigating the field by drip irrigation. Water falls dropby-drop at the position of roots. This can be the
most efficient method of irrigation in regions with
water scarcity. Water wastage is minimized by utilizing this method.
7. Dried neem leaves or turmeric can be used to
repel insects, pests, etc., which could harm the
stored grains.
8. To grow under optimal condition, rice requires
rainy season. As it is a Kharif crop, it is rice grown
in the period from July to October.
Supplement
Reading
Scope of
Science
REmEmBER
Before beginning this chapter, you should be able to:
• Recall the basic disciplines of science
• Understand the importance of science in everyday
phenomena
kEY IDEAS
After completing this chapter, you should be able to:
• Define science and know its branches
• Describe the techniques involved in a scientific methodology
• Apply scientific phenomena in everyday life
S.2
Supplement Reading
INTRODUCTION
From the time Humans came on earth, they were fascinated and curious about the natural
phenomena happening in the world (like the formation of a rainbow, birth of a child, changes in
the weather, etc.). People since time immemorial had been attempting to understand and explain
the world around them with all its processes and mechanisms. So, to cater to all these queries and
curiosity of mankind a specific branch of study developed called science. Science was an approach
to understand and explain the immediate world around us.
SCIENCE
The English term ‘science’ has been derived from the Latin term ‘scientia’ meaning ‘knowledge’.
It involves the study of natural world and how it works, by observing and experimenting. It is a
tool for searching and exploring the nature.
Branches of Science
Science is divided into many branches according to the area of study such as:
•• Natural science: Study of natural phenomenon (biological science, physical science, etc.)
•• Social science: Study of human behaviour and societies
•• Applied science: Applies scientific knowledge to develop technologies (e.g., engineering,
medicine, etc.)
•• Formal science: Concerned with logic, mathematics, etc.
How do Scientists Work?
A person engaged in observing and experimenting to gain knowledge about nature is called
scientist. Scientists follow a specific way for their innovations and this is called scientific method.
Scientific method involves a series of techniques such as:
••
••
••
••
••
••
Observation
Asking questions
Making hypotheses
Experimentation
Data analysis and making conclusions
Communicating the results
Observation
Observation involves receiving knowledge about a natural phenomenon through our senses and
recording the questions that we would like to answer.
Smell
Sight
Observation
Touch
Hearing
Taste
F i g . S . 1 Means through which observations can be made
Scope of Science
Asking Questions
After making an interesting observation, a scientific mind will be more curious to know
about it. And this curiosity would lead to asking questions, like what, why, how, when and
where?
What
Why
Questions
???
Which
When
How
F i g . S . 2 Types of questions asked after making an observation
Hypothesis
A hypothesis is a proposed explanation (guess) about a phenomenon on the basis of evidences as
a starting for further investigation. It is provisionally accepted and provides guidance for further
investigations, to find out the possible solutions for the problem you observed.
Hypothesis
Giving a guess
Solution 1
Solution 2
F i g . S . 3 Possible explanations for a hypothesis
Experimentation
To conduct experiments is one of the most important steps in the scientific method. It involves
testing of hypotheses made on the basis of observations. Experiments help in proving whether
hypothesis is right or wrong and also to formulate scientific theories.
F i g . S . 4 A student performing experiment in chemistry lab
S.3
S.4
Supplement Reading
Data Analysis and Conclusion
Results or data obtained after several trials of experiment are analyzed thoroughly. With this,
we come to a conclusion to know whether the hypothesis is right or wrong. If the experiment
results prove hypothesis, then the original question is answered otherwise the research continues,
forming new hypothesis and then conducting an experiment to test it.
Communicate Results
This step involves reporting the results of experiments to let others know about it. The results
could be presented as written reports or oral reports. Communicating the results among peers
may lead to a new question which may in turn lead to another investigation.
Accept
hypothesis
Observation
?
Asking
questions
Hypothesis
Make another
hypothesis
Experimentation
Analyse data Make report and
communicate
and make
with others
conclusions
¥
Reject
hypothesis
F i g . S . 5 Series of techniques followed in a scientific method
Work of a Scientist: An Example
The methodology followed by scientists while working on any hypothesis is explained in the
following steps.
•• When you place a plant near a window, after a few days, you can observe that the plant
bends towards the window.
~
This phenomenon makes you curious and you start asking questions like:
.
Why did the plant bend?
.
What is this phenomenon?
•• Based on the observation, you make a hypothesis about the possible reasons for this, such as:
~
Plant bends to get enough air.
or
~
Plant bends to get sunlight
•• Experiments were conducted to prove this, by placing the plants in different surroundings
and it was observed that in all the experiments, plant was bending towards the light
source.
Scope of Science
•• You analysed your data and came to a conclusion that it was sunlight that made the plant to
bend towards the window. And also, you found that all plants show these kinds of movements
in which they bend towards the light source.
•• After getting a proper conclusion you then make a report and present it, so that others will
get to know about it.
Famous Scientists and their Contributions
The world has witnessed some very great scientists since the historic times who have made a
huge impact on our understanding and reasoning of scientific phenomena. A few of these great
scientists are mentioned in this section along with their contributions.
Table S.1
Some famous scientists and their important contributions
Name
Year
Country
Contribution
Aristotle
(384–322 BC)
One of the earliest scientists
to classify living organisms
Charles Darwin
(1809–1882)
Gregor Mendel
(1822–1884)
James Watson
(b. 1928)
Robert Hooke
(1635–1703)
Sir Isaac Newton
(1643–1727)
Vikram Sarabhai
(1919–1971)
Ancient Greek
philosopher and
scientist
English naturalist,
geologist and
biologist
Founder of modern
science of genetics
Molecular biologist,
zoologist
English natural
philosopher
English physicist and
mathematician
Indian scientist
Albert Einstein
(1879–1955)
Thomas Alva Edison (1847–1931)
CV Raman
(1888–1970)
Dmitri Ivanovich
Mendeleev
(1834–1907)
Srinivasa Ramanujan (1887–1920)
Developed theories of
evolution
Developed laws of
inheritance
One of the codiscoverers of
the DNA structure.
Discovered cell
Formulated laws of motion
and universal gravitation
Widely regarded as the father
of India’s space programme.
Physicist
Contribution to modern
physics and best known for
the formula E = mc2
American inventor
Developed devices including
motion picture camera,
electric light bulb, etc.
Indian physicist
Carried out groundbreaking
work in the field of light
scattering
Russian chemist
Formulated periodic law
and created periodic table of
elements.
Indian mathematician Made substantial
contributions to
mathematical analysis number
theory, infinite series
S.5
S.6
Supplement Reading
Science in Everyday Life
Almost everything that makes our life easy is the outcome of science and scientific studies. It is
impossible to lead a life without science and its innovations. Science has gifted us with innovations such as:
i
•• It makes communication easy: Science has made the communication
possible and easy even if we are far away. Major inventions in this field
Info Box!
include mobile phones, internet, etc.
The first ever email was sent
•
•
Helps us to find cure for many diseases: Through science and its
in 1971.
innovations, we have found cure for millions of diseases. It has also become
The Internet took four years
possible to prevent some diseases through methods like vaccinations.
to reach its first 50 Million
Users.
Doctors are able to view inside the body with the help of various techniques,
such as x-rays, MRI scans, etc., and all of these are a result of science and
innovations.
•• Helps us to reduce the work load: Most of the work in everyday life can be done using
machines. Starting from using a calculator for simple calculations to a washing machine for
washing, everything is a product of science.
•• Makes our transportation easy: With the inventions of vehicles, it made our transportation
easy. After the invention of aeroplanes, it became possible for us to travel around the world
in less time.
Science for Human Welfare
The ultimate aim of science is human welfare. It has made our life comfortable. It has provided us
with many amenities of life. Science has made our life better than what it was in the past.
Table S.2 List of agricultural revolutions
i
Type of revolution
Goal
Green Revolution
Food grain production
White Revolution
Milk Production
Black Revolution
Petroleum Production
Blue Revolution
Fish Production
Silver Revolution
Egg/Poultry Production
•• N
ow we are able to produce more food to meet the requirements of
world through developments in agriculture, such as green revolution, blue
Info Box!
revolution, white revolution, etc.
Dr. Norman Borlaug is
•
•
We are able to travel across the world by land, air and water.
known as the ‘Father of
•
•
It is possible for us to dress better than our forefathers.
Green Revolution’ and Dr.
M.S.Swaminathan is the
•• We live in a better, safe place than in the past. Our houses, villages, town
‘Father of Indian Green
everything has improved through science.
Revolution’.
•• Science has also increased the lifespan of individuals through inventions in
the medical field.
•• Science has made us capable of surviving natural calamities to a great extent.
•• In fact all the basic requirements of life are now fulfilled by science and its innovations.
Scope of Science
S.7
Future of Science
1. What is science? What are the main branches?
S cience involves the study of natural world and how it works. It is a tool for searching and exploring the
nature by observing and experimenting. The various branches according to the area of study are:
•• Natural science: Study of natural phenomenon (biological science, physical science, etc.)
•• Social science: Study of human behaviour and societies
•• Applied science: Applies scientific knowledge to develop technologies (e.g., engineering, medicine,
etc.)
•• Formal science: Concerned with logics, mathematics, etc.
2. What does it mean by a hypothesis?
hypothesis is a proposed explanation (guess) about a phenomenon on the basis of evidences. It is the
A
initial stage of investigation. It is provisionally accepted and provides guidance for further investigations,
to find out the possible solutions of the problems you observed.
POINTS TO REMEMBER
•• Science involves the study of the natural world through observation and experimentation.
•• A scientific method involves a series of techniques to create an innovation.
•• The world has seen many great scientists, like Darwin and Newton whose discoveries have
made a huge contribution in improving the life on this planet.
•• Science have made our life much easy by its many inventions, like mobile phones, MRI
scans, trains, etc.
•• Still further researches are going on to make our lives better by more advanced technologies.
Quick Recap
Researches in science are going on to explore the hidden truths about the world. New technologies and tools provide new ways to discoveries. The main goal of all these studies is to
make the life comfortable on earth. Even research is going on to find out whether life is possible in other planets, such as mars. Through science we aim for a better future, keeping in mind
the studies should not harm the environment we live in and also it should not cause harm to
the human race and other life forms.
S.8
Supplement Reading
TEST YOUR CONCEPTS
Directions for questions 1 to 5: Fill in the blanks in each
question.
1. The scientist who introduced the formula E = mc2
is ________.
2. Cell was discovered by ________.
3. The proposed explanation or guess for the possible
solution for a problem observed is ________.
4. The first step in a scientific study is ________.
5. Study of human behaviour and societies comes
under ________ branch of science.
Directions for questions 6 to 11: For each of the following questions, four choices have been provided. Select
the correct alternative.
6. The branch of science related to developing technologies is
(a) Formal science
(b) Natural science
(c) Social science
(d) Applied science
(a) Observing a natural phenomenon
PRACTICE QUESTIONS
(b) Recording the questions to be solved.
about
the
observed
(d) Both (a) and (b)
8. Match the following
A Gregor Mendel
B Mendeleev
C CV Raman
D Sir Isaac Newton
i
ii
iii
iv
A
iv
iii
iv
iii
B
i
ii
iii
iv
C
ii
i
ii
ii
D
iii
iv
i
i
9. Which one of the following is a wrong statement?
(a) Science has made our communication easy.
(b)Green revolution and blue revolution are revolutions that have happened in IT industry.
(c) Thomas Alva Edison invented electric bulb.
(d)Vikram Sarabhai is considered as a father of
Indian space programme.
10. Indian mathematician who contributed to number
theory is
(a) Vikram Sarabhai
(b) CV Raman
(c) Gregor Mendel
(d) Srinivasa Ramanujan
11. Complete the table with the name of scientist or
his contribution accordingly.
7. Observation involves
(c)
Asking questions
phenomenon
(a)
(b)
(c)
(d)
Laws of motion
Indian physicist
Laws of inheritance
Periodic table
Scientist
_________________
Dimitri Ivanovich
Mendeleev
_________________
Albert Einstein
_________________
Charles Darwin
_________________
Contribution
Motion picture
camera
_________________
Infinite series
_____________
Universal gravitation
______________
DNA structure
MASTERING THE CONCEPTS
Knowledge and Understanding
1. Write a note on various advantages of science in
everyday life.
3. Name any three scientists from India and their
contributions.
2. Which is the last step in a scientific method?
4. Explain how scientists work with one suitable
example.
Scope of Science
S.9
TEST YOUR CONCEPTS
1. Albert Einstein
2. Robert Hooke
3. Hypothesis
4. Observation
5. Social science
6. (d)
7. (d)
8. (d)
9. (b)
10. (d)
11. Scientist
Thomas Alva Edison
Dmitri Ivanovich
Mendeleev
Srinivasa Ramanujan
Albert Einstein
Sir Isaac Newton
Charles Darwin
James Watson
Contribution
Motion picture camera
Periodic table and
periodic law
Infinite series
E = mc2
Universal gravitation
Theories of evolution
DNA structure
MASTERING THE CONCEPTS
1. Science plays a major role in everyday life. It has
made our communication easy, even if we are at
far away places. It has also made our transportation easy and comfortable. Through science, it is
now possible to treat millions of diseases, thereby
increasing the lifespan of people.
2. Communicating the results obtained after data
analysis to let others know about it is the last step
in a scientific method. The results can be presented as written or oral reports. Communicating
the results to peers may lead to new questions
every time which may in turn lead to another
investigation.
3. Vikram Sarabhai: Father of India’s space
programme.
Srinivasa Ramanujan: Indian mathematician
who made major contributions to number theory,
infinite series, etc.
CV Raman: Indian physicist who carried out
major work in the field of light scattering.
4. Scientists follow a specific pathway for their innovations, which is known as a scientific method. It
involves a series of techniques such as:
•• Observation
•• Asking questions
•• Making hypothesis
•• Experimentation
•• Data analysis and making conclusions
•• Communicating the results to others
Example:
•• Ram tried to germinate pea seed in water. He
observed that pea seed did not germinate.
•• He made hypothesis for the possible reasons
behind this.
~~ Hypothesis I—pea seeds do not require water
for germination
~~ Hypothesis II—pea seeds require air for
germination
~~ Hypothesis III—pea seeds require adequate
amount of both water and air for germination.
•• He conducted experiments to prove his
hypotheses. He tried to germinate pea seeds in
three different conditions.
~~ Exp I—placing pea seeds completely in water
without air for germination.
~~ Exp II—placing pea seeds in a plate without
water and provided only air for germination.
~~ Exp III—pea seeds are provided with both
water and air in sufficient amount.
•• The result obtained were
~~ Exp I—no seed germination
~~ Exp II—no seed germination
~~ Exp III—Seed germinated
•• He analyzed the experiment results and made
conclusion that pea seeds require both air and
water for germination.
H i n t s a n d E x p l a n at i o n
Knowledge and Understanding
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designua. 123rf.com; Page P1.14—Tefi. Shutterstock; Page P1.14—Designua. Shutterstock; Page P1.15—
snapgalleria. Shutterstock; Page P1.16—Alila Medical Media. Shutterstock; Page P1.18—Amit John. Pearson
India Education Services Pvt. Ltd; Page P1.19—Oxford Designers & Illustrators Ltd. Pearson Education Ltd
Chapter 2: Tissues and Body Movements
Page P2.1—Kateryna Kon. Shutterstock; Page P2.4—Honeyeyed. Shutterstock; Page P2.5—Power and
Syred/Science Photo Library; Page P2.6—Valentina Moraru. Shutterstock; Page P2.6—Science History
Images/Alamy Stock Photo; Page P2.7—Blamb; Page P2.8—Christopher Meade. Shutterstock; Page
P2.8—Jose Luis Calvo. Shutterstock; Page P2.8—Oxford Designers & Illustrators Ltd. Pearson Education
Ltd; Page P2.9—RomanenkoAlexey. Shutterstock; Page P2.9—Kateryna Kon. Shutterstock; Page P2.9—
Anna Jurkovska. Shutterstock; Page P2.10—Designua. Shutterstock; Page P2.10—tonaquatic19. 123rf.com;
Page P2.10—Designua. Shutterstock; Page P2.10—Jose Luis Calvo. Shutterstock; Page P2.10—Designua.
Shutterstock; Page P2.10—Jose Luis Calvo. Shutterstock; Page P2.11—848740. Shutterstock; Page P2.12—
Jubal Harshaw. Shutterstock; Page P2.12—royaltystockphoto.com. Shutterstock; Page P2.13—blickwinkel/
Alamy Stock Photo; Page P2.13—Arvind Singh Negi/Red Reef Design Studio. Pearson India Education
Services Pvt. Ltd; Page P2.14—elenabsl. Shutterstock; Page P2.15—Potapov Alexander. Shutterstock
Chapter 3: CLASSIFICATION of living organisms
Page P3.1—Volodymyr Burdiak. Shutterstock; Page P3.3—Maggy Meyer. Shutterstock; Page P3.3—Tatiana
Frank. Shutterstock; Page P3.7—blueringmedia. 123rf.com; Page P3.8—Lebendkulturen.de. Shutterstock;
Page P3.8—Lebendkulturen.de. Shutterstock; Page P3.8—Science Photo Library/Alamy Stock Photo; Page
P3.8—Simon Baylis. Shutterstock; Page P3.10—Lebendkulturen.de. Shutterstock; Page P3.10—phs2121.
123rf.com; Page P3.10—John Foxx Collection. Imagestate; Page P3.10—Dancestrokes. Shutterstock; Page
P3.10—Smile Fight. Shutterstock; Page P3.11—mychadre77. 123rf.com; Page P3.11—vapi. 123rf.com;
Page P3.11—Kondratuk Aleksei. Shutterstock; Page P3.11—D. Kucharski K. Kucharska. Shutterstock; Page
P3.11—Rattiya Thongdumhyu. Shutterstock; Page P3.11—123rf.com; Page P3.12—Aleksey Stemmer.
Shutterstock; Page P3.12—Masalski Maksim. Shutterstock; Page P3.12—Juniors Bildarchiv GmbH/Alamy
Stock Photo; Page P3.12—Maximilian Weinzierl/Alamy Stock Photo; Page P3.12—brulove. Shutterstock;
Page P3.12—Beth Swanson. Shutterstock; Page P3.13—Vlada Photo. Shutterstock; Page P3.13—Dirk
Ercken. Shutterstock; Page P3.13—Jerry Lin. Shutterstock; Page P3.13—Cultura Creative (RF)/Alamy Stock
Photo
PC.2
Photo Credits
Chapter 4: reproduction in Animals and plants
Page P4.1—Mopic. Shutterstock; Page P4.4—Alila Medical Media. Shutterstock; Page P4.5—Macrovector.
Shutterstock; Page P4.6—Double brain.Shutterstock; Page P4.6—587245. Shutterstock; Page P4.7—rendix_alextian. Shutterstock; Page P4.9—Sue McDonald. Shutterstock; Page P4.9—Vaida. Shutterstock; Page
P4.10—Dreamcreation. Shutterstock; Page P4.16—My Life Graphic. Shutterstock; Page P4.16—Anne
Kitzman. Shutterstock; Page P4.16—Madlen. Shutterstock; Page P4.17—123rf.com; Page P4.18—Mohd
Suhail. Pearson India Education Services Pvt. Ltd; Page P4.18—123rf.com; Page P4.19—KentaStudio.
Shutterstock; Page P4.20—Russell Kightley/Science Photo Library; Page P4.23—Brian A Jackson.
Shutterstock; Page P4.23—Mohd Suhail. Pearson India Education Services Pvt. Ltd; Page P4.24—Bogdan
Wankowicz. Shutterstock; Page P4.24—Bogdan Wankowicz. Shutterstock;
Chapter 5: Microorganisms and Human Health
Page P5.1—qcontrol. Shutterstock; Page P5.2—BSIP SA/Alamy Stock Photo; Page P5.2—Lightspring.
Shutterstock; Page P5.2—Lightspring. Shutterstock; Page P5.2—age fotostock/Alamy Stock Photo; Page
P5.2—blickwinkel/Alamy Stock Photo; Page P5.4—zigzagmtart. 123rf.com; Page P5.4—serezniy. 123rf.
com; Page P5.5—Kelly Marken. Shutterstock; Page P5.5—Victoria 1. Shutterstock; Page P5.7—Designua.
Shutterstock; Page P5.8—rob3000. 123rf.com; Page P5.10—Blaj Gabriel. Shutterstock; Page P5.10—ifong.
Shutterstock
Chapter 6: ecosystem and biodiversity
Page P6.1—sandermeertinsphotography. 123rf.com; Page P6.3—Shivani Anshuk. Pearson India Education
Services Pvt. Ltd; Page P6.4—Oxford Designers & Illustrators Ltd. Pearson Education Ltd; Page P6.4—HL
Studios. Pearson Education Ltd; Page P6.5—426. Shutterstock; Page P6.5—majeczka. Shutterstock; Page
P6.5—xtrekx. 123rf.com; Page P6.5—noomcpkstic. Shutterstock; Page P6.6—Rich Carey. Shutterstock;
Page P6.7—HL Studios. Pearson Education Ltd; Page P6.9—Erik Mandre. Shutterstock; Page P6.9—Gunter
Marx/Alamy Stock Photo; Page P6.10—lexaarts. Shutterstock; Page P6.11—Tupungato. Shutterstock; Page
P6.14—Anna Kompanieitseva. Shutterstock; Page P6.15—Emjay Smith. Shutterstock; Page P6.16—123rf.
com; Page P6.17—silentwings. Shutterstock; Page P6.17—anmbph. Shutterstock; Page P6.18—123rf.com;
Page P6.18—YuryZap. Shutterstock; Page P6.19—blickwinkel/Alamy Stock Photo; Page P6.20—Aleksandr
Denisyuk. Shutterstock; Page P6.20—Paul Goldstein. Imagestate; Page P6.20—123rf.com; Page P6.20—
dnivrab. 123rf.com
Chapter 7: Food production And Management
Page P7.1—monticello. Shutterstock; Page P7.2—123rf.com; Page P7.2—nata-lunata. Shutterstock; Page
P7.2—ve_ro_sa. Shutterstock; Page P7.4—arogant. Shutterstock; Page P7.4—Sergey Galushko/Alamy Stock
Photo; Page P7.4—Alexander Perepelitsyn/Alamy Stock Photo; Page P7.4—handsomepictures. Shutterstock;
Page P7.4—Showcake. Shutterstock; Page P7.4—Muellek Josef. Shutterstockv; Page P7.6—Tish1.
Shutterstock; Page P7.6—Tish1. Shutterstock; Page P7.7—Cornelia Pithart. Shutterstock; Page P7.7—123rf.
com; Page P7.8—stigmatize. Shutterstock; Page P7.9—MattLphotography; Page P7.9—Andrea Izzotti. 123rf.
com; Page P7.10—Dr. Morley Read. Shutterstock; Page P7.10—jovanjaric. 123rf.com; Page P7.10—macor.
123rf.com; Page P7.11—123rf.com; Page P7.11—YanLev. Shutterstock; Page P7.11—Visionsi. Shutterstock;
Page P7.11—fuyu liu. Shutterstock; Page P7.11—Alexander Sayenko. Shutterstock; Page P7.14—Mohd
Suhail. Pearson India Education Services Pvt. Ltd; Page P7.14—StudioSmart. Shutterstock; Page P7.15—Dr.
Morley Read. Shutterstock; Page P7.17—123rf.com; Page P7.18—Fotofermer. Shutterstock; Page P7.18—
monticello. Shutterstock; Page P7.19— Marie C Fields. Shutterstock; Page P7.19— dusanzidar. 123rf.com
Supplement Reading: scope of science
Page PS.1— Olivier Le Queinec. Shutterstock; Page PS.3— Tassh. Shutterstock;